[PATCH 2/2] drm/udl: Reading all edid blocks in DRM/UDL driver

[Alex Deucher]

On Thu, Oct 12, 2017 at 8:13 PM, Robert Tarasov
<tutankhamen at chromium.org> wrote:
> Now DRM/UDL driver retreives all edid data blocks instead of only base one.
> Previous approch could lead to improper initialization of video mode with
> certain monitors.
>
> Signed-off-by: Robert Tarasov <tutankhamen at chromium.org>

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

> ---
>  drivers/gpu/drm/udl/udl_connector.c | 106 +++++++++++++++++++++++-------------
>  1 file changed, 68 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/gpu/drm/udl/udl_connector.c b/drivers/gpu/drm/udl/udl_connector.c
> index 6a9250ac8f29..c3dc1fd20cb4 100644
> --- a/drivers/gpu/drm/udl/udl_connector.c
> +++ b/drivers/gpu/drm/udl/udl_connector.c
> @@ -17,42 +17,79 @@
>  #include "udl_connector.h"
>  #include "udl_drv.h"
>
> -/* dummy connector to just get EDID,
> -   all UDL appear to have a DVI-D */
> -
> -static u8 *udl_get_edid(struct udl_device *udl)
> +static bool udl_get_edid_block(struct udl_device *udl, int block_idx,
> +                                                          u8 *buff)
>  {
> -       u8 *block;
> -       char *rbuf;
>         int ret, i;
> +       u8 *read_buff;
>
> -       block = kmalloc(EDID_LENGTH, GFP_KERNEL);
> -       if (block == NULL)
> -               return NULL;
> -
> -       rbuf = kmalloc(2, GFP_KERNEL);
> -       if (rbuf == NULL)
> -               goto error;
> +       read_buff = kmalloc(2, GFP_KERNEL);
> +       if (!read_buff)
> +               return false;
>
>         for (i = 0; i < EDID_LENGTH; i++) {
> +               int bval = (i + block_idx * EDID_LENGTH) << 8;
>                 ret = usb_control_msg(udl->udev,
> -                                     usb_rcvctrlpipe(udl->udev, 0), (0x02),
> -                                     (0x80 | (0x02 << 5)), i << 8, 0xA1, rbuf, 2,
> -                                     HZ);
> +                                     usb_rcvctrlpipe(udl->udev, 0),
> +                                         (0x02), (0x80 | (0x02 << 5)), bval,
> +                                         0xA1, read_buff, 2, HZ);
>                 if (ret < 1) {
>                         DRM_ERROR("Read EDID byte %d failed err %x\n", i, ret);
> -                       goto error;
> +                       kfree(read_buff);
> +                       return false;
>                 }
> -               block[i] = rbuf[1];
> +               buff[i] = read_buff[1];
>         }
>
> -       kfree(rbuf);
> -       return block;
> +       kfree(read_buff);
> +       return true;
> +}
>
> -error:
> -       kfree(block);
> -       kfree(rbuf);
> -       return NULL;
> +static bool udl_get_edid(struct udl_device *udl, u8 **result_buff,
> +                        int *result_buff_size)
> +{
> +       int i, extensions;
> +       u8 *block_buff = NULL, *buff_ptr;
> +
> +       block_buff = kmalloc(EDID_LENGTH, GFP_KERNEL);
> +       if (block_buff == NULL)
> +               return false;
> +
> +       if (udl_get_edid_block(udl, 0, block_buff) &&
> +           memchr_inv(block_buff, 0, EDID_LENGTH)) {
> +               extensions = ((struct edid *)block_buff)->extensions;
> +               if (extensions > 0) {
> +                       /* we have to read all extensions one by one */
> +                       *result_buff_size = EDID_LENGTH * (extensions + 1);
> +                       *result_buff = kmalloc(*result_buff_size, GFP_KERNEL);
> +                       buff_ptr = *result_buff;
> +                       if (buff_ptr == NULL) {
> +                               kfree(block_buff);
> +                               return false;
> +                       }
> +                       memcpy(buff_ptr, block_buff, EDID_LENGTH);
> +                       kfree(block_buff);
> +                       buff_ptr += EDID_LENGTH;
> +                       for (i = 1; i < extensions; ++i) {
> +                               if (udl_get_edid_block(udl, i, buff_ptr)) {
> +                                       buff_ptr += EDID_LENGTH;
> +                               } else {
> +                                       kfree(*result_buff);
> +                                       *result_buff = NULL;
> +                                       return false;
> +                               }
> +                       }
> +                       return true;
> +               }
> +               /* we have only base edid block */
> +               *result_buff = block_buff;
> +               *result_buff_size = EDID_LENGTH;
> +               return true;
> +       }
> +
> +       kfree(block_buff);
> +
> +       return false;
>  }
>
>  static int udl_get_modes(struct drm_connector *connector)
> @@ -84,33 +121,26 @@ static int udl_mode_valid(struct drm_connector *connector,
>  static enum drm_connector_status
>  udl_detect(struct drm_connector *connector, bool force)
>  {
> -       struct edid *edid;
> +       u8 *edid_buff = NULL;
> +       int edid_buff_size = 0;
>         struct udl_device *udl = connector->dev->dev_private;
>         struct udl_drm_connector *udl_connector =
>                                         container_of(connector,
>                                         struct udl_drm_connector,
>                                         connector);
>
> +       /* cleanup previous edid */
>         if (udl_connector->edid != NULL) {
>                 kfree(udl_connector->edid);
>                 udl_connector->edid = NULL;
>         }
>
> -       edid = (struct edid *)udl_get_edid(udl);
> -       if (!edid || !memchr_inv(edid, 0, EDID_LENGTH))
> -               return connector_status_disconnected;
>
> -       udl_connector->edid = edid;
> -
> -       /*
> -        * We only read the main block, but if the monitor reports extension
> -        * blocks then the drm edid code expects them to be present, so patch
> -        * the extension count to 0.
> -        */
> -       udl_connector->edid->checksum +=
> -                       udl_connector->edid->extensions;
> -       udl_connector->edid->extensions = 0;
> +       if (!udl_get_edid(udl, &edid_buff, &edid_buff_size))
> +               return connector_status_disconnected;
>
> +       udl_connector->edid = (struct edid *)edid_buff;
> +
>         return connector_status_connected;
>  }
>
> --
> 2.15.0.rc0.271.g36b669edcc-goog
>
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