Re: [PATCH 3/3] drm/debugfs: add an "edid_override" file per connector

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Hi

On Thu, May 29, 2014 at 5:57 PM, Thomas Wood <thomas.wood@xxxxxxxxx> wrote:
> Add a file to debugfs for each connector that allows the edid data to be
> overridden.
>
> Signed-off-by: Thomas Wood <thomas.wood@xxxxxxxxx>
> ---
>  drivers/gpu/drm/drm_crtc.c         |  4 +++
>  drivers/gpu/drm/drm_debugfs.c      | 56 ++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_probe_helper.c |  9 +++++-
>  include/drm/drm_crtc.h             |  1 +
>  4 files changed, 69 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 59a2784..8543eac 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -3701,6 +3701,10 @@ 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 b57b614..2c666ba 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)
>
> @@ -295,6 +296,55 @@ 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;

Please copy "ubuf" before accessing it.. that's a user-space buffer.
> +
> +       if (len >= EDID_LENGTH) {

What? So if you write any invalid EDID, you reset it? That's wrong..
You should return an error in those cases.

> +               drm_mode_connector_update_edid_property(connector,
> +                                                       (struct edid *) ubuf);
> +               connector->override_edid = true;

Please check the error-code of update_edid_property() before setting
override_edid. You should also return that code if it is an error.

Furthermore, you must force override_edid = false; before calling
update_edid_property, otherwise writing twice to this file will
discard the second write (because update_edid_property() will do
nothing as override_edid is already true).

Last but not least, you *must* do an overflow check here!

> +       } else {
> +               if (connector->override_edid) {
> +                       connector->override_edid = false;
> +                       drm_mode_connector_update_edid_property(connector,
> +                                                               NULL);
> +               }
> +       }
> +
> +       return len;


Maybe you want something like this (untested!):


char *buf;
struct edid *edid;
int ret;

buf = memdup_user(ubuf, len);
if (IS_ERR(buf))
        return PTR_ERR(buf);

edid = buf;
connector->override_edid = false;

if (len == 5 && !strcmp(buf, "reset")) {
        ret = drm_mode_connector_update_edid_property(connector, NULL);
} else if (len < EDID_LENGTH || EDID_LENGTH * (1 + edid->extensions) > len) {
        ret = -EINVAL;
} else {
        ret = drm_mode_connector_update_edid_property(connector,
(struct edid*)buf);
        if (!ret)
                connector->override_edid = true;
}

kfree(buf);
return ret ? : len;



Thanks
David

> +}
> +
> +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,
> @@ -325,6 +375,12 @@ int drm_debugfs_connector_add(struct drm_connector *connector)
>         if (!ent)
>                 return -ENOMEM;
>
> +       /* edid */
> +       ent = debugfs_create_file("edid_override", S_IRUGO, root, connector,

IRUGO? Shouldn't this be writable for root?

> +                                 &drm_edid_fops);
> +       if (!ent)
> +               return -ENOMEM;
> +
>         return 0;
>  }
>
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index 79f07f2..1f0dc77 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 f04f4b9..11fce43 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -513,6 +513,7 @@ 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 */
>
> --
> 1.9.0
>
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> dri-devel@xxxxxxxxxxxxxxxxxxxxx
> http://lists.freedesktop.org/mailman/listinfo/dri-devel
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