Re: [PATCH] drm/udl: Refactor edid retreiving in UDL driver

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 12 Mar 2019, Robert Tarasov <tutankhamen@chromium.org> wrote:
> Now drm/udl driver uses drm_do_get_edid() function to retreive and
> validate all blocks of EDID data. Old approach had insufficient
> validation routine and had problems with retreiving of extra blocks

You'll also get support for debugfs and firmware loader EDID override
mechanisms for free.

Fixes: 75c65ee20ade ("drm/udl: Reading all edid blocks in DRM/UDL driver")

Signed-off-by missing!

> ---
>  drivers/gpu/drm/udl/udl_connector.c | 72 +++++------------------------
>  1 file changed, 11 insertions(+), 61 deletions(-)
>
> diff --git a/drivers/gpu/drm/udl/udl_connector.c b/drivers/gpu/drm/udl/udl_connector.c
> index c3dc1fd20cb4..c7f8ac2cdbe5 100644
> --- a/drivers/gpu/drm/udl/udl_connector.c
> +++ b/drivers/gpu/drm/udl/udl_connector.c
> @@ -17,18 +17,19 @@
>  #include "udl_connector.h"
>  #include "udl_drv.h"
>  
> -static bool udl_get_edid_block(struct udl_device *udl, int block_idx,
> -							   u8 *buff)
> +static int udl_get_edid_block(void *data, u8 *buf, unsigned int block,
> +				size_t len)
>  {
>  	int ret, i;
>  	u8 *read_buff;
> +	struct udl_device *udl = data;
>  
>  	read_buff = kmalloc(2, GFP_KERNEL);

A follow-up cleanup might be to switch to using "u8 read_buff[2];"
instead of kmallocing it.

I don't claim to understand how the usb stuff works, but otherwise the
patch looks good to me. Nice refactoring!

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

>  	if (!read_buff)
> -		return false;
> +		return -1;
>  
> -	for (i = 0; i < EDID_LENGTH; i++) {
> -		int bval = (i + block_idx * EDID_LENGTH) << 8;
> +	for (i = 0; i < len; i++) {
> +		int bval = (i + block * EDID_LENGTH) << 8;
>  		ret = usb_control_msg(udl->udev,
>  				      usb_rcvctrlpipe(udl->udev, 0),
>  					  (0x02), (0x80 | (0x02 << 5)), bval,
> @@ -36,60 +37,13 @@ static bool udl_get_edid_block(struct udl_device *udl, int block_idx,
>  		if (ret < 1) {
>  			DRM_ERROR("Read EDID byte %d failed err %x\n", i, ret);
>  			kfree(read_buff);
> -			return false;
> +			return -1;
>  		}
> -		buff[i] = read_buff[1];
> +		buf[i] = read_buff[1];
>  	}
>  
>  	kfree(read_buff);
> -	return true;
> -}
> -
> -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;
> +	return 0;
>  }
>  
>  static int udl_get_modes(struct drm_connector *connector)
> @@ -121,8 +75,6 @@ static int udl_mode_valid(struct drm_connector *connector,
>  static enum drm_connector_status
>  udl_detect(struct drm_connector *connector, bool force)
>  {
> -	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,
> @@ -135,12 +87,10 @@ udl_detect(struct drm_connector *connector, bool force)
>  		udl_connector->edid = NULL;
>  	}
>  
> -
> -	if (!udl_get_edid(udl, &edid_buff, &edid_buff_size))
> +	udl_connector->edid = drm_do_get_edid(connector, udl_get_edid_block, udl);
> +	if (!udl_connector->edid)
>  		return connector_status_disconnected;
>  
> -	udl_connector->edid = (struct edid *)edid_buff;
> -	
>  	return connector_status_connected;
>  }

-- 
Jani Nikula, Intel Open Source Graphics Center
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