OSCL-LXR linux-6.0.1/​drivers/​gpu/​drm/​drm_probe_helper.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /*
  * Copyright (c) 2006-2008 Intel Corporation
  * Copyright (c) 2007 Dave Airlie <airlied@linux.ie>
  *
  * DRM core CRTC related functions
  *
  * Permission to use, copy, modify, distribute, and sell this software and its
  * documentation for any purpose is hereby granted without fee, provided that
  * the above copyright notice appear in all copies and that both that copyright
  * notice and this permission notice appear in supporting documentation, and
  * that the name of the copyright holders not be used in advertising or
  * publicity pertaining to distribution of the software without specific,
  * written prior permission.  The copyright holders make no representations
  * about the suitability of this software for any purpose.  It is provided "as
  * is" without express or implied warranty.
  *
  * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
  * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
  * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
  * OF THIS SOFTWARE.
  *
  * Authors:
  *      Keith Packard
  *  Eric Anholt <eric@anholt.net>
  *      Dave Airlie <airlied@linux.ie>
  *      Jesse Barnes <jesse.barnes@intel.com>
  */
 
 #include <linux/export.h>
 #include <linux/moduleparam.h>
 
 #include <drm/drm_bridge.h>
 #include <drm/drm_client.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_modeset_helper_vtables.h>
 #include <drm/drm_print.h>
 #include <drm/drm_probe_helper.h>
 #include <drm/drm_sysfs.h>
 
 #include "drm_crtc_helper_internal.h"
 
 /**
  * DOC: output probing helper overview
  *
  * This library provides some helper code for output probing. It provides an
  * implementation of the core &drm_connector_funcs.fill_modes interface with
  * drm_helper_probe_single_connector_modes().
  *
  * It also provides support for polling connectors with a work item and for
  * generic hotplug interrupt handling where the driver doesn't or cannot keep
  * track of a per-connector hpd interrupt.
  *
  * This helper library can be used independently of the modeset helper library.
  * Drivers can also overwrite different parts e.g. use their own hotplug
  * handling code to avoid probing unrelated outputs.
  *
  * The probe helpers share the function table structures with other display
  * helper libraries. See &struct drm_connector_helper_funcs for the details.
  */
 
 static bool drm_kms_helper_poll = true;
 module_param_named(poll, drm_kms_helper_poll, bool, 0600);
 
 static enum drm_mode_status
 drm_mode_validate_flag(const struct drm_display_mode *mode,
                int flags)
 {
     if ((mode->flags & DRM_MODE_FLAG_INTERLACE) &&
         !(flags & DRM_MODE_FLAG_INTERLACE))
         return MODE_NO_INTERLACE;
 
     if ((mode->flags & DRM_MODE_FLAG_DBLSCAN) &&
         !(flags & DRM_MODE_FLAG_DBLSCAN))
         return MODE_NO_DBLESCAN;
 
     if ((mode->flags & DRM_MODE_FLAG_3D_MASK) &&
         !(flags & DRM_MODE_FLAG_3D_MASK))
         return MODE_NO_STEREO;
 
     return MODE_OK;
 }
 
 static int
 drm_mode_validate_pipeline(struct drm_display_mode *mode,
                struct drm_connector *connector,
                struct drm_modeset_acquire_ctx *ctx,
                enum drm_mode_status *status)
 {
     struct drm_device *dev = connector->dev;
     struct drm_encoder *encoder;
     int ret;
 
     /* Step 1: Validate against connector */
     ret = drm_connector_mode_valid(connector, mode, ctx, status);
     if (ret || *status != MODE_OK)
         return ret;
 
     /* Step 2: Validate against encoders and crtcs */
     drm_connector_for_each_possible_encoder(connector, encoder) {
         struct drm_bridge *bridge;
         struct drm_crtc *crtc;
 
         *status = drm_encoder_mode_valid(encoder, mode);
         if (*status != MODE_OK) {
             /* No point in continuing for crtc check as this encoder
              * will not accept the mode anyway. If all encoders
              * reject the mode then, at exit, ret will not be
              * MODE_OK. */
             continue;
         }
 
         bridge = drm_bridge_chain_get_first_bridge(encoder);
         *status = drm_bridge_chain_mode_valid(bridge,
                               &connector->display_info,
                               mode);
         if (*status != MODE_OK) {
             /* There is also no point in continuing for crtc check
              * here. */
             continue;
         }
 
         drm_for_each_crtc(crtc, dev) {
             if (!drm_encoder_crtc_ok(encoder, crtc))
                 continue;
 
             *status = drm_crtc_mode_valid(crtc, mode);
             if (*status == MODE_OK) {
                 /* If we get to this point there is at least
                  * one combination of encoder+crtc that works
                  * for this mode. Lets return now. */
                 return 0;
             }
         }
     }
 
     return 0;
 }
 
 static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
 {
     struct drm_cmdline_mode *cmdline_mode;
     struct drm_display_mode *mode;
 
     cmdline_mode = &connector->cmdline_mode;
     if (!cmdline_mode->specified)
         return 0;
 
     /* Only add a GTF mode if we find no matching probed modes */
     list_for_each_entry(mode, &connector->probed_modes, head) {
         if (mode->hdisplay != cmdline_mode->xres ||
             mode->vdisplay != cmdline_mode->yres)
             continue;
 
         if (cmdline_mode->refresh_specified) {
             /* The probed mode's vrefresh is set until later */
             if (drm_mode_vrefresh(mode) != cmdline_mode->refresh)
                 continue;
         }
 
         /* Mark the matching mode as being preferred by the user */
         mode->type |= DRM_MODE_TYPE_USERDEF;
         return 0;
     }
 
     mode = drm_mode_create_from_cmdline_mode(connector->dev,
                          cmdline_mode);
     if (mode == NULL)
         return 0;
 
     drm_mode_probed_add(connector, mode);
     return 1;
 }
 
 enum drm_mode_status drm_crtc_mode_valid(struct drm_crtc *crtc,
                      const struct drm_display_mode *mode)
 {
     const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
 
     if (!crtc_funcs || !crtc_funcs->mode_valid)
         return MODE_OK;
 
     return crtc_funcs->mode_valid(crtc, mode);
 }
 
 enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
                         const struct drm_display_mode *mode)
 {
     const struct drm_encoder_helper_funcs *encoder_funcs =
         encoder->helper_private;
 
     if (!encoder_funcs || !encoder_funcs->mode_valid)
         return MODE_OK;
 
     return encoder_funcs->mode_valid(encoder, mode);
 }
 
 int
 drm_connector_mode_valid(struct drm_connector *connector,
              struct drm_display_mode *mode,
              struct drm_modeset_acquire_ctx *ctx,
              enum drm_mode_status *status)
 {
     const struct drm_connector_helper_funcs *connector_funcs =
         connector->helper_private;
     int ret = 0;
 
     if (!connector_funcs)
         *status = MODE_OK;
     else if (connector_funcs->mode_valid_ctx)
         ret = connector_funcs->mode_valid_ctx(connector, mode, ctx,
                               status);
     else if (connector_funcs->mode_valid)
         *status = connector_funcs->mode_valid(connector, mode);
     else
         *status = MODE_OK;
 
     return ret;
 }
 
 #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
 /**
  * drm_kms_helper_poll_enable - re-enable output polling.
  * @dev: drm_device
  *
  * This function re-enables the output polling work, after it has been
  * temporarily disabled using drm_kms_helper_poll_disable(), for example over
  * suspend/resume.
  *
  * Drivers can call this helper from their device resume implementation. It is
  * not an error to call this even when output polling isn't enabled.
  *
  * Note that calls to enable and disable polling must be strictly ordered, which
  * is automatically the case when they're only call from suspend/resume
  * callbacks.
  */
 void drm_kms_helper_poll_enable(struct drm_device *dev)
 {
     bool poll = false;
     struct drm_connector *connector;
     struct drm_connector_list_iter conn_iter;
     unsigned long delay = DRM_OUTPUT_POLL_PERIOD;
 
     if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll)
         return;
 
     drm_connector_list_iter_begin(dev, &conn_iter);
     drm_for_each_connector_iter(connector, &conn_iter) {
         if (connector->polled & (DRM_CONNECTOR_POLL_CONNECT |
                      DRM_CONNECTOR_POLL_DISCONNECT))
             poll = true;
     }
     drm_connector_list_iter_end(&conn_iter);
 
     if (dev->mode_config.delayed_event) {
         /*
          * FIXME:
          *
          * Use short (1s) delay to handle the initial delayed event.
          * This delay should not be needed, but Optimus/nouveau will
          * fail in a mysterious way if the delayed event is handled as
          * soon as possible like it is done in
          * drm_helper_probe_single_connector_modes() in case the poll
          * was enabled before.
          */
         poll = true;
         delay = HZ;
     }
 
     if (poll)
         schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_enable);
 
 static enum drm_connector_status
 drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
 {
     const struct drm_connector_helper_funcs *funcs = connector->helper_private;
     struct drm_modeset_acquire_ctx ctx;
     int ret;
 
     drm_modeset_acquire_init(&ctx, 0);
 
 retry:
     ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex, &ctx);
     if (!ret) {
         if (funcs->detect_ctx)
             ret = funcs->detect_ctx(connector, &ctx, force);
         else if (connector->funcs->detect)
             ret = connector->funcs->detect(connector, force);
         else
             ret = connector_status_connected;
     }
 
     if (ret == -EDEADLK) {
         drm_modeset_backoff(&ctx);
         goto retry;
     }
 
     if (WARN_ON(ret < 0))
         ret = connector_status_unknown;
 
     if (ret != connector->status)
         connector->epoch_counter += 1;
 
     drm_modeset_drop_locks(&ctx);
     drm_modeset_acquire_fini(&ctx);
 
     return ret;
 }
 
 /**
  * drm_helper_probe_detect - probe connector status
  * @connector: connector to probe
  * @ctx: acquire_ctx, or NULL to let this function handle locking.
  * @force: Whether destructive probe operations should be performed.
  *
  * This function calls the detect callbacks of the connector.
  * This function returns &drm_connector_status, or
  * if @ctx is set, it might also return -EDEADLK.
  */
 int
 drm_helper_probe_detect(struct drm_connector *connector,
             struct drm_modeset_acquire_ctx *ctx,
             bool force)
 {
     const struct drm_connector_helper_funcs *funcs = connector->helper_private;
     struct drm_device *dev = connector->dev;
     int ret;
 
     if (!ctx)
         return drm_helper_probe_detect_ctx(connector, force);
 
     ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
     if (ret)
         return ret;
 
     if (funcs->detect_ctx)
         ret = funcs->detect_ctx(connector, ctx, force);
     else if (connector->funcs->detect)
         ret = connector->funcs->detect(connector, force);
     else
         ret = connector_status_connected;
 
     if (ret != connector->status)
         connector->epoch_counter += 1;
 
     return ret;
 }
 EXPORT_SYMBOL(drm_helper_probe_detect);
 
 static int drm_helper_probe_get_modes(struct drm_connector *connector)
 {
     const struct drm_connector_helper_funcs *connector_funcs =
         connector->helper_private;
     int count;
 
     count = connector_funcs->get_modes(connector);
 
     /*
      * Fallback for when DDC probe failed in drm_get_edid() and thus skipped
      * override/firmware EDID.
      */
     if (count == 0 && connector->status == connector_status_connected)
         count = drm_add_override_edid_modes(connector);
 
     return count;
 }
 
 static int __drm_helper_update_and_validate(struct drm_connector *connector,
                         uint32_t maxX, uint32_t maxY,
                         struct drm_modeset_acquire_ctx *ctx)
 {
     struct drm_device *dev = connector->dev;
     struct drm_display_mode *mode;
     int mode_flags = 0;
     int ret;
 
     drm_connector_list_update(connector);
 
     if (connector->interlace_allowed)
         mode_flags |= DRM_MODE_FLAG_INTERLACE;
     if (connector->doublescan_allowed)
         mode_flags |= DRM_MODE_FLAG_DBLSCAN;
     if (connector->stereo_allowed)
         mode_flags |= DRM_MODE_FLAG_3D_MASK;
 
     list_for_each_entry(mode, &connector->modes, head) {
         if (mode->status != MODE_OK)
             continue;
 
         mode->status = drm_mode_validate_driver(dev, mode);
         if (mode->status != MODE_OK)
             continue;
 
         mode->status = drm_mode_validate_size(mode, maxX, maxY);
         if (mode->status != MODE_OK)
             continue;
 
         mode->status = drm_mode_validate_flag(mode, mode_flags);
         if (mode->status != MODE_OK)
             continue;
 
         ret = drm_mode_validate_pipeline(mode, connector, ctx,
                          &mode->status);
         if (ret) {
             drm_dbg_kms(dev,
                     "drm_mode_validate_pipeline failed: %d\n",
                     ret);
 
             if (drm_WARN_ON_ONCE(dev, ret != -EDEADLK))
                 mode->status = MODE_ERROR;
             else
                 return -EDEADLK;
         }
 
         if (mode->status != MODE_OK)
             continue;
         mode->status = drm_mode_validate_ycbcr420(mode, connector);
     }
 
     return 0;
 }
 
 /**
  * drm_helper_probe_single_connector_modes - get complete set of display modes
  * @connector: connector to probe
  * @maxX: max width for modes
  * @maxY: max height for modes
  *
  * Based on the helper callbacks implemented by @connector in struct
  * &drm_connector_helper_funcs try to detect all valid modes.  Modes will first
  * be added to the connector's probed_modes list, then culled (based on validity
  * and the @maxX, @maxY parameters) and put into the normal modes list.
  *
  * Intended to be used as a generic implementation of the
  * &drm_connector_funcs.fill_modes() vfunc for drivers that use the CRTC helpers
  * for output mode filtering and detection.
  *
  * The basic procedure is as follows
  *
  * 1. All modes currently on the connector's modes list are marked as stale
  *
  * 2. New modes are added to the connector's probed_modes list with
  *    drm_mode_probed_add(). New modes start their life with status as OK.
  *    Modes are added from a single source using the following priority order.
  *
  *    - &drm_connector_helper_funcs.get_modes vfunc
  *    - if the connector status is connector_status_connected, standard
  *      VESA DMT modes up to 1024x768 are automatically added
  *      (drm_add_modes_noedid())
  *
  *    Finally modes specified via the kernel command line (video=...) are
  *    added in addition to what the earlier probes produced
  *    (drm_helper_probe_add_cmdline_mode()). These modes are generated
  *    using the VESA GTF/CVT formulas.
  *
  * 3. Modes are moved from the probed_modes list to the modes list. Potential
  *    duplicates are merged together (see drm_connector_list_update()).
  *    After this step the probed_modes list will be empty again.
  *
  * 4. Any non-stale mode on the modes list then undergoes validation
  *
  *    - drm_mode_validate_basic() performs basic sanity checks
  *    - drm_mode_validate_size() filters out modes larger than @maxX and @maxY
  *      (if specified)
  *    - drm_mode_validate_flag() checks the modes against basic connector
  *      capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
  *    - the optional &drm_connector_helper_funcs.mode_valid or
  *      &drm_connector_helper_funcs.mode_valid_ctx helpers can perform driver
  *      and/or sink specific checks
  *    - the optional &drm_crtc_helper_funcs.mode_valid,
  *      &drm_bridge_funcs.mode_valid and &drm_encoder_helper_funcs.mode_valid
  *      helpers can perform driver and/or source specific checks which are also
  *      enforced by the modeset/atomic helpers
  *
  * 5. Any mode whose status is not OK is pruned from the connector's modes list,
  *    accompanied by a debug message indicating the reason for the mode's
  *    rejection (see drm_mode_prune_invalid()).
  *
  * Returns:
  * The number of modes found on @connector.
  */
 int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
                         uint32_t maxX, uint32_t maxY)
 {
     struct drm_device *dev = connector->dev;
     struct drm_display_mode *mode;
     int count = 0, ret;
     enum drm_connector_status old_status;
     struct drm_modeset_acquire_ctx ctx;
 
     WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
 
     drm_modeset_acquire_init(&ctx, 0);
 
     DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
             connector->name);
 
 retry:
     ret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
     if (ret == -EDEADLK) {
         drm_modeset_backoff(&ctx);
         goto retry;
     } else
         WARN_ON(ret < 0);
 
     /* set all old modes to the stale state */
     list_for_each_entry(mode, &connector->modes, head)
         mode->status = MODE_STALE;
 
     old_status = connector->status;
 
     if (connector->force) {
         if (connector->force == DRM_FORCE_ON ||
             connector->force == DRM_FORCE_ON_DIGITAL)
             connector->status = connector_status_connected;
         else
             connector->status = connector_status_disconnected;
         if (connector->funcs->force)
             connector->funcs->force(connector);
     } else {
         ret = drm_helper_probe_detect(connector, &ctx, true);
 
         if (ret == -EDEADLK) {
             drm_modeset_backoff(&ctx);
             goto retry;
         } else if (WARN(ret < 0, "Invalid return value %i for connector detection\n", ret))
             ret = connector_status_unknown;
 
         connector->status = ret;
     }
 
     /*
      * Normally either the driver's hpd code or the poll loop should
      * pick up any changes and fire the hotplug event. But if
      * userspace sneaks in a probe, we might miss a change. Hence
      * check here, and if anything changed start the hotplug code.
      */
     if (old_status != connector->status) {
         DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
                   connector->base.id,
                   connector->name,
                   drm_get_connector_status_name(old_status),
                   drm_get_connector_status_name(connector->status));
 
         /*
          * The hotplug event code might call into the fb
          * helpers, and so expects that we do not hold any
          * locks. Fire up the poll struct instead, it will
          * disable itself again.
          */
         dev->mode_config.delayed_event = true;
         if (dev->mode_config.poll_enabled)
             schedule_delayed_work(&dev->mode_config.output_poll_work,
                           0);
     }
 
     /* Re-enable polling in case the global poll config changed. */
     if (drm_kms_helper_poll != dev->mode_config.poll_running)
         drm_kms_helper_poll_enable(dev);
 
     dev->mode_config.poll_running = drm_kms_helper_poll;
 
     if (connector->status == connector_status_disconnected) {
         DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
             connector->base.id, connector->name);
         drm_connector_update_edid_property(connector, NULL);
         drm_mode_prune_invalid(dev, &connector->modes, false);
         goto exit;
     }
 
     count = drm_helper_probe_get_modes(connector);
 
     if (count == 0 && (connector->status == connector_status_connected ||
                connector->status == connector_status_unknown)) {
         count = drm_add_modes_noedid(connector, 1024, 768);
 
         /*
          * Section 4.2.2.6 (EDID Corruption Detection) of the DP 1.4a
          * Link CTS specifies that 640x480 (the official "failsafe"
          * mode) needs to be the default if there's no EDID.
          */
         if (connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort)
             drm_set_preferred_mode(connector, 640, 480);
     }
     count += drm_helper_probe_add_cmdline_mode(connector);
     if (count != 0) {
         ret = __drm_helper_update_and_validate(connector, maxX, maxY, &ctx);
         if (ret == -EDEADLK) {
             drm_modeset_backoff(&ctx);
             goto retry;
         }
     }
 
     drm_mode_prune_invalid(dev, &connector->modes, true);
 
     /*
      * Displayport spec section 5.2.1.2 ("Video Timing Format") says that
      * all detachable sinks shall support 640x480 @60Hz as a fail safe
      * mode. If all modes were pruned, perhaps because they need more
      * lanes or a higher pixel clock than available, at least try to add
      * in 640x480.
      */
     if (list_empty(&connector->modes) &&
         connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) {
         count = drm_add_modes_noedid(connector, 640, 480);
         ret = __drm_helper_update_and_validate(connector, maxX, maxY, &ctx);
         if (ret == -EDEADLK) {
             drm_modeset_backoff(&ctx);
             goto retry;
         }
         drm_mode_prune_invalid(dev, &connector->modes, true);
     }
 
 exit:
     drm_modeset_drop_locks(&ctx);
     drm_modeset_acquire_fini(&ctx);
 
     if (list_empty(&connector->modes))
         return 0;
 
     drm_mode_sort(&connector->modes);
 
     DRM_DEBUG_KMS("[CONNECTOR:%d:%s] probed modes :\n", connector->base.id,
             connector->name);
     list_for_each_entry(mode, &connector->modes, head) {
         drm_mode_set_crtcinfo(mode, CRTC_INTERLACE_HALVE_V);
         drm_mode_debug_printmodeline(mode);
     }
 
     return count;
 }
 EXPORT_SYMBOL(drm_helper_probe_single_connector_modes);
 
 /**
  * drm_kms_helper_hotplug_event - fire off KMS hotplug events
  * @dev: drm_device whose connector state changed
  *
  * This function fires off the uevent for userspace and also calls the
  * output_poll_changed function, which is most commonly used to inform the fbdev
  * emulation code and allow it to update the fbcon output configuration.
  *
  * Drivers should call this from their hotplug handling code when a change is
  * detected. Note that this function does not do any output detection of its
  * own, like drm_helper_hpd_irq_event() does - this is assumed to be done by the
  * driver already.
  *
  * This function must be called from process context with no mode
  * setting locks held.
  *
  * If only a single connector has changed, consider calling
  * drm_kms_helper_connector_hotplug_event() instead.
  */
 void drm_kms_helper_hotplug_event(struct drm_device *dev)
 {
     /* send a uevent + call fbdev */
     drm_sysfs_hotplug_event(dev);
     if (dev->mode_config.funcs->output_poll_changed)
         dev->mode_config.funcs->output_poll_changed(dev);
 
     drm_client_dev_hotplug(dev);
 }
 EXPORT_SYMBOL(drm_kms_helper_hotplug_event);
 
 /**
  * drm_kms_helper_connector_hotplug_event - fire off a KMS connector hotplug event
  * @connector: drm_connector which has changed
  *
  * This is the same as drm_kms_helper_hotplug_event(), except it fires a more
  * fine-grained uevent for a single connector.
  */
 void drm_kms_helper_connector_hotplug_event(struct drm_connector *connector)
 {
     struct drm_device *dev = connector->dev;
 
     /* send a uevent + call fbdev */
     drm_sysfs_connector_hotplug_event(connector);
     if (dev->mode_config.funcs->output_poll_changed)
         dev->mode_config.funcs->output_poll_changed(dev);
 
     drm_client_dev_hotplug(dev);
 }
 EXPORT_SYMBOL(drm_kms_helper_connector_hotplug_event);
 
 static void output_poll_execute(struct work_struct *work)
 {
     struct delayed_work *delayed_work = to_delayed_work(work);
     struct drm_device *dev = container_of(delayed_work, struct drm_device, mode_config.output_poll_work);
     struct drm_connector *connector;
     struct drm_connector_list_iter conn_iter;
     enum drm_connector_status old_status;
     bool repoll = false, changed;
     u64 old_epoch_counter;
 
     if (!dev->mode_config.poll_enabled)
         return;
 
     /* Pick up any changes detected by the probe functions. */
     changed = dev->mode_config.delayed_event;
     dev->mode_config.delayed_event = false;
 
     if (!drm_kms_helper_poll)
         goto out;
 
     if (!mutex_trylock(&dev->mode_config.mutex)) {
         repoll = true;
         goto out;
     }
 
     drm_connector_list_iter_begin(dev, &conn_iter);
     drm_for_each_connector_iter(connector, &conn_iter) {
         /* Ignore forced connectors. */
         if (connector->force)
             continue;
 
         /* Ignore HPD capable connectors and connectors where we don't
          * want any hotplug detection at all for polling. */
         if (!connector->polled || connector->polled == DRM_CONNECTOR_POLL_HPD)
             continue;
 
         old_status = connector->status;
         /* if we are connected and don't want to poll for disconnect
            skip it */
         if (old_status == connector_status_connected &&
             !(connector->polled & DRM_CONNECTOR_POLL_DISCONNECT))
             continue;
 
         repoll = true;
 
         old_epoch_counter = connector->epoch_counter;
         connector->status = drm_helper_probe_detect(connector, NULL, false);
         if (old_epoch_counter != connector->epoch_counter) {
             const char *old, *new;
 
             /*
              * The poll work sets force=false when calling detect so
              * that drivers can avoid to do disruptive tests (e.g.
              * when load detect cycles could cause flickering on
              * other, running displays). This bears the risk that we
              * flip-flop between unknown here in the poll work and
              * the real state when userspace forces a full detect
              * call after receiving a hotplug event due to this
              * change.
              *
              * Hence clamp an unknown detect status to the old
              * value.
              */
             if (connector->status == connector_status_unknown) {
                 connector->status = old_status;
                 continue;
             }
 
             old = drm_get_connector_status_name(old_status);
             new = drm_get_connector_status_name(connector->status);
 
             DRM_DEBUG_KMS("[CONNECTOR:%d:%s] "
                       "status updated from %s to %s\n",
                       connector->base.id,
                       connector->name,
                       old, new);
             DRM_DEBUG_KMS("[CONNECTOR:%d:%s] epoch counter %llu -> %llu\n",
                       connector->base.id, connector->name,
                       old_epoch_counter, connector->epoch_counter);
 
             changed = true;
         }
     }
     drm_connector_list_iter_end(&conn_iter);
 
     mutex_unlock(&dev->mode_config.mutex);
 
 out:
     if (changed)
         drm_kms_helper_hotplug_event(dev);
 
     if (repoll)
         schedule_delayed_work(delayed_work, DRM_OUTPUT_POLL_PERIOD);
 }
 
 /**
  * drm_kms_helper_is_poll_worker - is %current task an output poll worker?
  *
  * Determine if %current task is an output poll worker.  This can be used
  * to select distinct code paths for output polling versus other contexts.
  *
  * One use case is to avoid a deadlock between the output poll worker and
  * the autosuspend worker wherein the latter waits for polling to finish
  * upon calling drm_kms_helper_poll_disable(), while the former waits for
  * runtime suspend to finish upon calling pm_runtime_get_sync() in a
  * connector ->detect hook.
  */
 bool drm_kms_helper_is_poll_worker(void)
 {
     struct work_struct *work = current_work();
 
     return work && work->func == output_poll_execute;
 }
 EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);
 
 /**
  * drm_kms_helper_poll_disable - disable output polling
  * @dev: drm_device
  *
  * This function disables the output polling work.
  *
  * Drivers can call this helper from their device suspend implementation. It is
  * not an error to call this even when output polling isn't enabled or already
  * disabled. Polling is re-enabled by calling drm_kms_helper_poll_enable().
  *
  * Note that calls to enable and disable polling must be strictly ordered, which
  * is automatically the case when they're only call from suspend/resume
  * callbacks.
  */
 void drm_kms_helper_poll_disable(struct drm_device *dev)
 {
     if (!dev->mode_config.poll_enabled)
         return;
     cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_disable);
 
 /**
  * drm_kms_helper_poll_init - initialize and enable output polling
  * @dev: drm_device
  *
  * This function initializes and then also enables output polling support for
  * @dev. Drivers which do not have reliable hotplug support in hardware can use
  * this helper infrastructure to regularly poll such connectors for changes in
  * their connection state.
  *
  * Drivers can control which connectors are polled by setting the
  * DRM_CONNECTOR_POLL_CONNECT and DRM_CONNECTOR_POLL_DISCONNECT flags. On
  * connectors where probing live outputs can result in visual distortion drivers
  * should not set the DRM_CONNECTOR_POLL_DISCONNECT flag to avoid this.
  * Connectors which have no flag or only DRM_CONNECTOR_POLL_HPD set are
  * completely ignored by the polling logic.
  *
  * Note that a connector can be both polled and probed from the hotplug handler,
  * in case the hotplug interrupt is known to be unreliable.
  */
 void drm_kms_helper_poll_init(struct drm_device *dev)
 {
     INIT_DELAYED_WORK(&dev->mode_config.output_poll_work, output_poll_execute);
     dev->mode_config.poll_enabled = true;
 
     drm_kms_helper_poll_enable(dev);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_init);
 
 /**
  * drm_kms_helper_poll_fini - disable output polling and clean it up
  * @dev: drm_device
  */
 void drm_kms_helper_poll_fini(struct drm_device *dev)
 {
     if (!dev->mode_config.poll_enabled)
         return;
 
     dev->mode_config.poll_enabled = false;
     cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_fini);
 
 static bool check_connector_changed(struct drm_connector *connector)
 {
     struct drm_device *dev = connector->dev;
     enum drm_connector_status old_status;
     u64 old_epoch_counter;
 
     /* Only handle HPD capable connectors. */
     drm_WARN_ON(dev, !(connector->polled & DRM_CONNECTOR_POLL_HPD));
 
     drm_WARN_ON(dev, !mutex_is_locked(&dev->mode_config.mutex));
 
     old_status = connector->status;
     old_epoch_counter = connector->epoch_counter;
     connector->status = drm_helper_probe_detect(connector, NULL, false);
 
     if (old_epoch_counter == connector->epoch_counter) {
         drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Same epoch counter %llu\n",
                 connector->base.id,
                 connector->name,
                 connector->epoch_counter);
 
         return false;
     }
 
     drm_dbg_kms(dev, "[CONNECTOR:%d:%s] status updated from %s to %s\n",
             connector->base.id,
             connector->name,
             drm_get_connector_status_name(old_status),
             drm_get_connector_status_name(connector->status));
 
     drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Changed epoch counter %llu => %llu\n",
             connector->base.id,
             connector->name,
             old_epoch_counter,
             connector->epoch_counter);
 
     return true;
 }
 
 /**
  * drm_connector_helper_hpd_irq_event - hotplug processing
  * @connector: drm_connector
  *
  * Drivers can use this helper function to run a detect cycle on a connector
  * which has the DRM_CONNECTOR_POLL_HPD flag set in its &polled member.
  *
  * This helper function is useful for drivers which can track hotplug
  * interrupts for a single connector. Drivers that want to send a
  * hotplug event for all connectors or can't track hotplug interrupts
  * per connector need to use drm_helper_hpd_irq_event().
  *
  * This function must be called from process context with no mode
  * setting locks held.
  *
  * Note that a connector can be both polled and probed from the hotplug
  * handler, in case the hotplug interrupt is known to be unreliable.
  *
  * Returns:
  * A boolean indicating whether the connector status changed or not
  */
 bool drm_connector_helper_hpd_irq_event(struct drm_connector *connector)
 {
     struct drm_device *dev = connector->dev;
     bool changed;
 
     mutex_lock(&dev->mode_config.mutex);
     changed = check_connector_changed(connector);
     mutex_unlock(&dev->mode_config.mutex);
 
     if (changed) {
         drm_kms_helper_connector_hotplug_event(connector);
         drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Sent hotplug event\n",
                 connector->base.id,
                 connector->name);
     }
 
     return changed;
 }
 EXPORT_SYMBOL(drm_connector_helper_hpd_irq_event);
 
 /**
  * drm_helper_hpd_irq_event - hotplug processing
  * @dev: drm_device
  *
  * Drivers can use this helper function to run a detect cycle on all connectors
  * which have the DRM_CONNECTOR_POLL_HPD flag set in their &polled member. All
  * other connectors are ignored, which is useful to avoid reprobing fixed
  * panels.
  *
  * This helper function is useful for drivers which can't or don't track hotplug
  * interrupts for each connector.
  *
  * Drivers which support hotplug interrupts for each connector individually and
  * which have a more fine-grained detect logic can use
  * drm_connector_helper_hpd_irq_event(). Alternatively, they should bypass this
  * code and directly call drm_kms_helper_hotplug_event() in case the connector
  * state changed.
  *
  * This function must be called from process context with no mode
  * setting locks held.
  *
  * Note that a connector can be both polled and probed from the hotplug handler,
  * in case the hotplug interrupt is known to be unreliable.
  *
  * Returns:
  * A boolean indicating whether the connector status changed or not
  */
 bool drm_helper_hpd_irq_event(struct drm_device *dev)
 {
     struct drm_connector *connector, *first_changed_connector = NULL;
     struct drm_connector_list_iter conn_iter;
     int changed = 0;
 
     if (!dev->mode_config.poll_enabled)
         return false;
 
     mutex_lock(&dev->mode_config.mutex);
     drm_connector_list_iter_begin(dev, &conn_iter);
     drm_for_each_connector_iter(connector, &conn_iter) {
         /* Only handle HPD capable connectors. */
         if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
             continue;
 
         if (check_connector_changed(connector)) {
             if (!first_changed_connector) {
                 drm_connector_get(connector);
                 first_changed_connector = connector;
             }
 
             changed++;
         }
     }
     drm_connector_list_iter_end(&conn_iter);
     mutex_unlock(&dev->mode_config.mutex);
 
     if (changed == 1)
         drm_kms_helper_connector_hotplug_event(first_changed_connector);
     else if (changed > 0)
         drm_kms_helper_hotplug_event(dev);
 
     if (first_changed_connector)
         drm_connector_put(first_changed_connector);
 
     return changed;
 }
 EXPORT_SYMBOL(drm_helper_hpd_irq_event);
 
 /**
  * drm_connector_helper_get_modes_from_ddc - Updates the connector's EDID
  *                                           property from the connector's
  *                                           DDC channel
  * @connector: The connector
  *
  * Returns:
  * The number of detected display modes.
  *
  * Uses a connector's DDC channel to retrieve EDID data and update the
  * connector's EDID property and display modes. Drivers can use this
  * function to implement struct &drm_connector_helper_funcs.get_modes
  * for connectors with a DDC channel.
  */
 int drm_connector_helper_get_modes_from_ddc(struct drm_connector *connector)
 {
     struct edid *edid;
     int count = 0;
 
     if (!connector->ddc)
         return 0;
 
     edid = drm_get_edid(connector, connector->ddc);
 
     // clears property if EDID is NULL
     drm_connector_update_edid_property(connector, edid);
 
     if (edid) {
         count = drm_add_edid_modes(connector, edid);
         kfree(edid);
     }
 
     return count;
 }
 EXPORT_SYMBOL(drm_connector_helper_get_modes_from_ddc);
 
 /**
  * drm_connector_helper_get_modes - Read EDID and update connector.
  * @connector: The connector
  *
  * Read the EDID using drm_edid_read() (which requires that connector->ddc is
  * set), and update the connector using the EDID.
  *
  * This can be used as the "default" connector helper .get_modes() hook if the
  * driver does not need any special processing. This is sets the example what
  * custom .get_modes() hooks should do regarding EDID read and connector update.
  *
  * Returns: Number of modes.
  */
 int drm_connector_helper_get_modes(struct drm_connector *connector)
 {
     const struct drm_edid *drm_edid;
     int count;
 
     drm_edid = drm_edid_read(connector);
 
     /*
      * Unconditionally update the connector. If the EDID was read
      * successfully, fill in the connector information derived from the
      * EDID. Otherwise, if the EDID is NULL, clear the connector
      * information.
      */
     count = drm_edid_connector_update(connector, drm_edid);
 
     drm_edid_free(drm_edid);
 
     return count;
 }
 EXPORT_SYMBOL(drm_connector_helper_get_modes);

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