[PATCH v2 2/2] drm/debugfs: add an "edid_override" file per connector

[Alex Deucher]

On Wed, Jun 18, 2014 at 12:52 PM, Thomas Wood <thomas.wood at intel.com> wrote:
> Add a file to debugfs for each connector to allow the EDID to be
> overridden.
>
> v2: Copy ubuf before accessing it and reject invalid length data. (David
>     Herrmann)
>     Ensure override_edid is reset when a new EDID value is written.
>     (David Herrmann)
>     Fix the debugfs file permissions. (David Herrmann)
>
> Signed-off-by: Thomas Wood <thomas.wood at intel.com>

One minor nit below, but either way:

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/drm_crtc.c         |  4 +++
>  drivers/gpu/drm/drm_debugfs.c      | 68 ++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_probe_helper.c |  9 ++++-
>  include/drm/drm_crtc.h             |  1 +
>  4 files changed, 81 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index fdb69f7..4b3bbc4 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -3916,6 +3916,10 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
>         struct drm_device *dev = connector->dev;
>         int ret, size;
>
> +       /* ignore requests to set edid when overridden */
> +       if (connector->override_edid)
> +               return 0;
> +
>         if (connector->edid_blob_ptr)
>                 drm_property_destroy_blob(dev, connector->edid_blob_ptr);
>
> diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
> index 8ab3f3e..13bd429 100644
> --- a/drivers/gpu/drm/drm_debugfs.c
> +++ b/drivers/gpu/drm/drm_debugfs.c
> @@ -35,6 +35,7 @@
>  #include <linux/slab.h>
>  #include <linux/export.h>
>  #include <drm/drmP.h>
> +#include <drm/drm_edid.h>
>
>  #if defined(CONFIG_DEBUG_FS)
>
> @@ -304,6 +305,67 @@ static ssize_t connector_write(struct file *file, const char __user *ubuf,
>         return len;
>  }
>
> +static int edid_show(struct seq_file *m, void *data)
> +{
> +       struct drm_connector *connector = m->private;
> +       struct drm_property_blob *edid = connector->edid_blob_ptr;
> +
> +       if (connector->override_edid && edid)
> +               seq_write(m, edid->data, edid->length);
> +
> +       return 0;
> +}
> +
> +static int edid_open(struct inode *inode, struct file *file)
> +{
> +       struct drm_connector *dev = inode->i_private;
> +
> +       return single_open(file, edid_show, dev);
> +}
> +
> +static ssize_t edid_write(struct file *file, const char __user *ubuf,
> +                         size_t len, loff_t *offp)
> +{
> +       struct seq_file *m = file->private_data;
> +       struct drm_connector *connector = m->private;
> +       char *buf;
> +       struct edid *edid;
> +       int ret;
> +
> +       buf = memdup_user(ubuf, len);
> +       if (IS_ERR(buf))
> +               return PTR_ERR(buf);
> +
> +       edid = (struct edid *) buf;
> +
> +       if (len == 5 && !strncmp(buf, "reset", 5)) {
> +               connector->override_edid = false;
> +               ret = drm_mode_connector_update_edid_property(connector, NULL);
> +       } else if (len < EDID_LENGTH ||
> +                  EDID_LENGTH * (1 + edid->extensions) > len)
> +               ret = -EINVAL;
> +       else {
> +               connector->override_edid = false;

Might be worth doing some minimal validation of the EDID (e.g., make
sure it has a valid header).

Alex

> +               ret = drm_mode_connector_update_edid_property(connector, edid);
> +               if (!ret)
> +                       connector->override_edid = true;
> +       }
> +
> +       kfree(buf);
> +
> +       return (ret) ? ret : len;
> +}
> +
> +static const struct file_operations drm_edid_fops = {
> +       .owner = THIS_MODULE,
> +       .open = edid_open,
> +       .read = seq_read,
> +       .llseek = seq_lseek,
> +       .release = single_release,
> +       .write = edid_write
> +};
> +
> +
>  static const struct file_operations drm_connector_fops = {
>         .owner = THIS_MODULE,
>         .open = connector_open,
> @@ -333,6 +395,12 @@ int drm_debugfs_connector_add(struct drm_connector *connector)
>         if (!ent)
>                 goto error;
>
> +       /* edid */
> +       ent = debugfs_create_file("edid_override", S_IRUGO | S_IWUSR, root,
> +                                 connector, &drm_edid_fops);
> +       if (!ent)
> +               goto error;
> +
>         return 0;
>
>  error:
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index d22676b..db7d250 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -130,7 +130,14 @@ static int drm_helper_probe_single_connector_modes_merge_bits(struct drm_connect
>         count = drm_load_edid_firmware(connector);
>         if (count == 0)
>  #endif
> -               count = (*connector_funcs->get_modes)(connector);
> +       {
> +               if (connector->override_edid) {
> +                       struct edid *edid = (struct edid *) connector->edid_blob_ptr->data;
> +
> +                       count = drm_add_edid_modes(connector, edid);
> +               } else
> +                       count = (*connector_funcs->get_modes)(connector);
> +       }
>
>         if (count == 0 && connector->status == connector_status_connected)
>                 count = drm_add_modes_noedid(connector, 1024, 768);
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 67a33bc..d09b471 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -537,6 +537,7 @@ struct drm_connector {
>
>         /* forced on connector */
>         enum drm_connector_force force;
> +       bool override_edid;
>         uint32_t encoder_ids[DRM_CONNECTOR_MAX_ENCODER];
>         struct drm_encoder *encoder; /* currently active encoder */
>
> --
> 1.9.3
>
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