On Wed, Feb 01, 2017 at 10:58:43AM +0000, Peter Senna Tschudin wrote:

Hi Archit,

On 01 February, 2017 10:44 CET, Archit Taneja [off-list ref] wrote:

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On 01/30/2017 10:35 PM, Jani Nikula wrote:

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On Sat, 28 Jan 2017, Peter Senna Tschudin [off-list ref] wrote:

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On Thu, Jan 05, 2017 at 01:18:47PM +0530, Archit Taneja wrote:
Hi Archit,

Thank you for the comments!

[...]

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+	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()?

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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.

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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

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in the future.

My concern is that for almost one year now, every time I fix something
one or two new requests are made. I'm happy to fix the driver, but I
want a list of the changes that are required to get it upstream, before
I make more changes. Can we agree on exactly what is preventing this
driver to get upstream? Then I'll fix it.

I think addressing this edid reading question post-merge is perfectly
fine. Aside, want to keep maintaing your stuff as part of the drm-misc
group, with the drivers-in-misc experiment?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch