Hi Daniel,

It would be great to have this patch in weston 2.0.
We made a similar patch to fix this issue for Renesas Gen3 boards.

Best regards

Emre Ucan
Software Group I (ADITG/SW1)

Tel. +49 5121 49 6937

> -----Original Message-----
> From: wayland-devel [mailto:wayland-devel-
> [email protected]] On Behalf Of Daniel Stone
> Sent: Dienstag, 14. Februar 2017 17:12
> To: [email protected]
> Subject: [PATCH weston v6] compositor-drm: Ignore non-KMS devices
> 
> Given that we can have render-only devices, or vgem in a class of its
> own, ignore any non-KMS devices in compositor-drm's device selection.
> For x86 platforms, this is mostly a non-issue since we look at the udev
> boot_vga issue, but other architectures which lack this, and have
> multiple KMS devices present, will hit this.
> 
> Signed-off-by: Daniel Stone <[email protected]>
> Reviewed-by: Emil Velikov <[email protected]>
> Reported-by: Thierry Reding <[email protected]>
> Reported-by: Daniel Vetter <[email protected]>
> ---
>  libweston/compositor-drm.c | 145
> ++++++++++++++++++++++++++++++++-------------
>  1 file changed, 103 insertions(+), 42 deletions(-)
> 
> This is now R-b, but I'm going to leave it on the list to decide whether
> or not we should ship it; it's awfully close to release day.
> 
> v6: Elaborate comment further. Properly initialise and test for old FD.
>     Use correct filename in all cases. Don't overwrite 'id' in corner
>     cases.
> 
> diff --git a/libweston/compositor-drm.c b/libweston/compositor-drm.c
> index 2a80c6d79..f364648c7 100644
> --- a/libweston/compositor-drm.c
> +++ b/libweston/compositor-drm.c
> @@ -1506,36 +1506,15 @@ on_drm_input(int fd, uint32_t mask, void *data)
>  }
> 
>  static int
> -init_drm(struct drm_backend *b, struct udev_device *device)
> +init_kms_caps(struct drm_backend *b)
>  {
> -     const char *filename, *sysnum;
>       uint64_t cap;
> -     int fd, ret;
> +     int ret;
>       clockid_t clk_id;
> 
> -     sysnum = udev_device_get_sysnum(device);
> -     if (sysnum)
> -             b->drm.id = atoi(sysnum);
> -     if (!sysnum || b->drm.id < 0) {
> -             weston_log("cannot get device sysnum\n");
> -             return -1;
> -     }
> -
> -     filename = udev_device_get_devnode(device);
> -     fd = weston_launcher_open(b->compositor->launcher, filename,
> O_RDWR);
> -     if (fd < 0) {
> -             /* Probably permissions error */
> -             weston_log("couldn't open %s, skipping\n",
> -                     udev_device_get_devnode(device));
> -             return -1;
> -     }
> -
> -     weston_log("using %s\n", filename);
> -
> -     b->drm.fd = fd;
> -     b->drm.filename = strdup(filename);
> +     weston_log("using %s\n", b->drm.filename);
> 
> -     ret = drmGetCap(fd, DRM_CAP_TIMESTAMP_MONOTONIC, &cap);
> +     ret = drmGetCap(b->drm.fd, DRM_CAP_TIMESTAMP_MONOTONIC,
> &cap);
>       if (ret == 0 && cap == 1)
>               clk_id = CLOCK_MONOTONIC;
>       else
> @@ -1547,13 +1526,13 @@ init_drm(struct drm_backend *b, struct
> udev_device *device)
>               return -1;
>       }
> 
> -     ret = drmGetCap(fd, DRM_CAP_CURSOR_WIDTH, &cap);
> +     ret = drmGetCap(b->drm.fd, DRM_CAP_CURSOR_WIDTH, &cap);
>       if (ret == 0)
>               b->cursor_width = cap;
>       else
>               b->cursor_width = 64;
> 
> -     ret = drmGetCap(fd, DRM_CAP_CURSOR_HEIGHT, &cap);
> +     ret = drmGetCap(b->drm.fd, DRM_CAP_CURSOR_HEIGHT, &cap);
>       if (ret == 0)
>               b->cursor_height = cap;
>       else
> @@ -2939,12 +2918,68 @@ session_notify(struct wl_listener *listener, void
> *data)
>       };
>  }
> 
> +/**
> + * Determines whether or not a device is capable of modesetting. If
> successful,
> + * sets b->drm.fd and b->drm.filename to the opened device.
> + */
> +static bool
> +drm_device_is_kms(struct drm_backend *b, struct udev_device *device)
> +{
> +     const char *filename = udev_device_get_devnode(device);
> +     const char *sysnum = udev_device_get_sysnum(device);
> +     drmModeRes *res;
> +     int id, fd;
> +
> +     if (!filename)
> +             return false;
> +
> +     fd = weston_launcher_open(b->compositor->launcher, filename,
> O_RDWR);
> +     if (fd < 0)
> +             return false;
> +
> +     res = drmModeGetResources(fd);
> +     if (!res)
> +             goto out_fd;
> +
> +     if (res->count_crtcs <= 0 || res->count_connectors <= 0 ||
> +         res->count_encoders <= 0)
> +             goto out_res;
> +
> +     if (sysnum)
> +             id = atoi(sysnum);
> +     if (!sysnum || id < 0) {
> +             weston_log("couldn't get sysnum for device %s\n",
> filename);
> +             goto out_res;
> +     }
> +
> +     /* We can be called successfully on multiple devices; if we have,
> +      * clean up old entries. */
> +     if (b->drm.fd >= 0)
> +             weston_launcher_close(b->compositor->launcher, b-
> >drm.fd);
> +     free(b->drm.filename);
> +
> +     b->drm.fd = fd;
> +     b->drm.id = id;
> +     b->drm.filename = strdup(filename);
> +
> +     return true;
> +
> +out_res:
> +     drmModeFreeResources(res);
> +out_fd:
> +     weston_launcher_close(b->compositor->launcher, fd);
> +     return false;
> +}
> +
>  /*
>   * Find primary GPU
>   * Some systems may have multiple DRM devices attached to a single seat.
> This
>   * function loops over all devices and tries to find a PCI device with the
>   * boot_vga sysfs attribute set to 1.
>   * If no such device is found, the first DRM device reported by udev is used.
> + * Devices are also vetted to make sure they are are capable of
> modesetting,
> + * rather than pure render nodes (GPU with no display), or pure
> + * memory-allocation devices (VGEM).
>   */
>  static struct udev_device*
>  find_primary_gpu(struct drm_backend *b, const char *seat)
> @@ -2961,6 +2996,8 @@ find_primary_gpu(struct drm_backend *b, const
> char *seat)
>       udev_enumerate_scan_devices(e);
>       drm_device = NULL;
>       udev_list_entry_foreach(entry, udev_enumerate_get_list_entry(e))
> {
> +             bool is_boot_vga = false;
> +
>               path = udev_list_entry_get_name(entry);
>               device = udev_device_new_from_syspath(b->udev, path);
>               if (!device)
> @@ -2977,20 +3014,46 @@ find_primary_gpu(struct drm_backend *b, const
> char *seat)
>                                                               "pci", NULL);
>               if (pci) {
>                       id = udev_device_get_sysattr_value(pci,
> "boot_vga");
> -                     if (id && !strcmp(id, "1")) {
> -                             if (drm_device)
> -                                     udev_device_unref(drm_device);
> -                             drm_device = device;
> -                             break;
> -                     }
> +                     if (id && !strcmp(id, "1"))
> +                             is_boot_vga = true;
>               }
> 
> -             if (!drm_device)
> -                     drm_device = device;
> -             else
> +             /* If we already have a modesetting-capable device, and this
> +              * device isn't our boot-VGA device, we aren't going to use
> +              * it. */
> +             if (!is_boot_vga && drm_device) {
> +                     udev_device_unref(device);
> +                     continue;
> +             }
> +
> +             /* Make sure this device is actually capable of modesetting;
> +              * if this call succeeds, b->drm.{fd,filename} will be set,
> +              * and any old values freed. */
> +             if (!drm_device_is_kms(b, device)) {
>                       udev_device_unref(device);
> +                     continue;
> +             }
> +
> +             /* There can only be one boot_vga device, and we try to use
> it
> +              * at all costs. */
> +             if (is_boot_vga) {
> +                     if (drm_device)
> +                             udev_device_unref(drm_device);
> +                     drm_device = device;
> +                     break;
> +             }
> +
> +             /* Per the (!is_boot_vga && drm_device) test above, we
> only
> +              * trump existing saved devices with boot-VGA devices, so if
> +              * we end up here, this must be the first device we've seen.
> */
> +             assert(!drm_device);
> +             drm_device = device;
>       }
> 
> +     /* If we're returning a device to use, we must have an open FD for
> +      * it. */
> +     assert(!!drm_device == (b->drm.fd >= 0));
> +
>       udev_enumerate_unref(e);
>       return drm_device;
>  }
> @@ -3193,7 +3256,6 @@ drm_backend_create(struct weston_compositor
> *compositor,
>       struct drm_backend *b;
>       struct udev_device *drm_device;
>       struct wl_event_loop *loop;
> -     const char *path;
>       const char *seat_id = default_seat;
>       int ret;
> 
> @@ -3203,6 +3265,8 @@ drm_backend_create(struct weston_compositor
> *compositor,
>       if (b == NULL)
>               return NULL;
> 
> +     b->drm.fd = -1;
> +
>       /*
>        * KMS support for hardware planes cannot properly synchronize
>        * without nuclear page flip. Without nuclear/atomic, hw plane
> @@ -3246,9 +3310,8 @@ drm_backend_create(struct weston_compositor
> *compositor,
>               weston_log("no drm device found\n");
>               goto err_udev;
>       }
> -     path = udev_device_get_syspath(drm_device);
> 
> -     if (init_drm(b, drm_device) < 0) {
> +     if (init_kms_caps(b) < 0) {
>               weston_log("failed to initialize kms\n");
>               goto err_udev_dev;
>       }
> @@ -3283,7 +3346,7 @@ drm_backend_create(struct weston_compositor
> *compositor,
>       b->connector = config->connector;
> 
>       if (create_outputs(b, drm_device) < 0) {
> -             weston_log("failed to create output for %s\n", path);
> +             weston_log("failed to create output for %s\n", b-
> >drm.filename);
>               goto err_udev_input;
>       }
> 
> @@ -3292,8 +3355,6 @@ drm_backend_create(struct weston_compositor
> *compositor,
>       if (!b->cursors_are_broken)
>               compositor->capabilities |= WESTON_CAP_CURSOR_PLANE;
> 
> -     path = NULL;
> -
>       loop = wl_display_get_event_loop(compositor->wl_display);
>       b->drm_source =
>               wl_event_loop_add_fd(loop, b->drm.fd,
> --
> 2.11.0
> 
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