[Intel-gfx] [PATCH 05/15] drm/i915/bios: abstract finding the panel sequence block

[Jani Nikula]

On Tue, 05 Jan 2016, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Mon, Dec 21, 2015 at 03:10:56PM +0200, Jani Nikula wrote:
>> Make the whole thing easier to read.
>> 
>> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_bios.c | 76 +++++++++++++++++++++------------------
>>  1 file changed, 42 insertions(+), 34 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
>> index 7393596df37d..9511a5341562 100644
>> --- a/drivers/gpu/drm/i915/intel_bios.c
>> +++ b/drivers/gpu/drm/i915/intel_bios.c
>> @@ -697,7 +697,7 @@ parse_psr(struct drm_i915_private *dev_priv, const struct bdb_header *bdb)
>>  	dev_priv->vbt.psr.tp2_tp3_wakeup_time = psr_table->tp2_tp3_wakeup_time;
>>  }
>>  
>> -static u8 *goto_next_sequence(u8 *data, int *size)
>> +static u8 *goto_next_sequence(u8 *data, u16 *size)
>>  {
>>  	u16 len;
>>  	int tmp = *size;
>> @@ -818,15 +818,52 @@ parse_mipi_config(struct drm_i915_private *dev_priv,
>>  	dev_priv->vbt.dsi.panel_id = MIPI_DSI_GENERIC_PANEL_ID;
>>  }
>>  
>> +/* Find the sequence block and size for the given panel. */
>> +static const u8 *
>> +find_panel_sequence_block(const struct bdb_mipi_sequence *sequence,
>> +			  u16 panel_id, u16 *seq_size)
>> +{
>> +	u32 total = get_blocksize(sequence);
>> +	const u8 *data = &sequence->data[0];
>> +	u8 current_id;
>> +	u16 current_size;
>> +	int index = 0;
>> +	int i;
>> +
>> +	for (i = 0; i < MAX_MIPI_CONFIGURATIONS && index + 3 < total; i++) {
>
> Commit message should mention that you make the parsin more robust and
> ensure we don't walk over the end of the allocated buffer.

Agreed. Although it's implied in the Signed-off-by line. ;)

>
>> +		current_id = *(data + index);
>> +		index++;
>> +
>> +		current_size = *((const u16 *)(data + index));
>> +		index += 2;
>> +
>> +		if (index + current_size > total) {
>> +			DRM_ERROR("Invalid sequence block\n");
>> +			return NULL;
>> +		}
>> +
>> +		if (current_id == panel_id) {
>> +			*seq_size = current_size;
>> +			return data + index;
>> +		}
>> +
>> +		index += current_size;
>> +	}
>> +
>> +	DRM_ERROR("Sequence block detected but no valid configuration\n");
>> +
>> +	return NULL;
>> +}
>> +
>>  static void
>>  parse_mipi_sequence(struct drm_i915_private *dev_priv,
>>  		    const struct bdb_header *bdb)
>>  {
>>  	const struct bdb_mipi_sequence *sequence;
>>  	const u8 *seq_data;
>> +	u16 seq_size;
>>  	u8 *data;
>>  	u16 block_size;
>> -	int i, panel_id, seq_size;
>>  
>>  	/* Only our generic panel driver uses the sequence block. */
>>  	if (dev_priv->vbt.dsi.panel_id != MIPI_DSI_GENERIC_PANEL_ID)
>> @@ -853,40 +890,11 @@ parse_mipi_sequence(struct drm_i915_private *dev_priv,
>>  	 */
>>  	dev_priv->vbt.dsi.seq_version = sequence->version;
>>  
>> -	seq_data = &sequence->data[0];
>> -
>> -	/*
>> -	 * sequence block is variable length and hence we need to parse and
>> -	 * get the sequence data for specific panel id
>> -	 */
>> -	for (i = 0; i < MAX_MIPI_CONFIGURATIONS; i++) {
>> -		panel_id = *seq_data;
>> -		seq_size = *((u16 *) (seq_data + 1));
>> -		if (panel_id == panel_type)
>> -			break;
>> -
>> -		/* skip the sequence including seq header of 3 bytes */
>> -		seq_data = seq_data + 3 + seq_size;
>> -		if ((seq_data - &sequence->data[0]) > block_size) {
>> -			DRM_ERROR("Sequence start is beyond sequence block size, corrupted sequence block\n");
>> -			return;
>> -		}
>> -	}
>> -
>> -	if (i == MAX_MIPI_CONFIGURATIONS) {
>> -		DRM_ERROR("Sequence block detected but no valid configuration\n");
>> +	seq_data = find_panel_sequence_block(sequence, panel_type, &seq_size);
>> +	if (!seq_data)
>>  		return;
>> -	}
>> -
>> -	/* check if found sequence is completely within the sequence block
>> -	 * just being paranoid */
>> -	if (seq_size > block_size) {
>> -		DRM_ERROR("Corrupted sequence/size, bailing out\n");
>> -		return;
>> -	}
>>  
>> -	/* skip the panel id(1 byte) and seq size(2 bytes) */
>> -	dev_priv->vbt.dsi.data = kmemdup(seq_data + 3, seq_size, GFP_KERNEL);
>> +	dev_priv->vbt.dsi.data = kmemdup(seq_data, seq_size, GFP_KERNEL);
>
> Should dropping the +3 be in a separate patch?

Really I'd rather not if you don't mind. The end result is the same, but
I'd have to think the function over again just to add a throwaway
intermediate step. Unless I just replace the return statement with
"return data + index - 3" which would feel a bit silly, don't you think?

BR,
Jani.

>
> Otherwise looks good, with the above 2 addressed
>
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>
>>  	if (!dev_priv->vbt.dsi.data)
>>  		return;
>>  
>> -- 
>> 2.1.4
>> 
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>> Intel-gfx at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Jani Nikula, Intel Open Source Technology Center