Re: [PATCH V7 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

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On 01/30/2017 10:35 PM, Jani Nikula wrote:
On Sat, 28 Jan 2017, Peter Senna Tschudin <peter.senna@xxxxxxxxxxxxx> wrote:
On Thu, Jan 05, 2017 at 01:18:47PM +0530, Archit Taneja wrote:
Hi Archit,

Thank you for the comments!

[...]
+	total_size = (block[EDID_EXT_BLOCK_CNT] + 1) * EDID_LENGTH;
+	if (total_size > EDID_LENGTH) {
+		kfree(block);
+		block = kmalloc(total_size, GFP_KERNEL);
+		if (!block)
+			return NULL;
+
+		/* Yes, read the entire buffer, and do not skip the first
+		 * EDID_LENGTH bytes.
+		 */

Is this the reason why you aren't using drm_do_get_edid()?

Yes, for some hw specific reason, it is necessary to read the entire
EDID buffer starting from 0, not block by block.

Hrmh, I'm planning on moving the edid override and firmware edid
mechanisms at the drm_do_get_edid() level to be able to truly and
transparently use a different edid. Currently, they're only used for
modes, really, and lead to some info retrieved from overrides, some from
the real edid. This kind of hacks will bypass the override/firmware edid
mechanisms then too. :(

It seems like there is a HW issue which prevents them from reading EDID
from an offset. So, I'm not sure if it is a hack or a HW limitation.

One way around this would be to hide the HW requirement in the
get_edid_block func pointer passed to drm_do_get_edid(). This
would, however, result in more i2c reads (equal to # of extension
blocks) than what the patch currently does.

Peter, if you think doing extra EDID reads isn't too costly on your
platform, you could consider using drm_do_get_edid(). If not, I guess
you'll miss out on the additional functionality Jani is going to add
in the future.

Thanks,
Archit



BR,
Jani.



[...]

I fixed all your other suggestions. Thank you!
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