Re: [PATCH] efifb: BGRT: Add check for new BGRT status field rotation bits

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 11-06-19 16:04, Ard Biesheuvel wrote:
> On Mon, 10 Jun 2019 at 17:12, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>>
>> On Wed, 29 May 2019 at 17:46, Hans de Goede <hdegoede@redhat.com> wrote:
>>>
>>> Starting with ACPI 6.2 bits 1 and 2 of the BGRT status field are no longer
>>> reserved. These bits are now used to indicate if the image needs to be
>>> rotated before being displayed.
>>>
>>> The efifb code does not support rotating the image before copying it to
>>> the screen.
>>>
>>> This commit adds a check for these new bits and if they are set leaves the
>>> fb contents as is instead of trying to use the un-rotated BGRT image.
>>>
>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>
>> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>
> 
> BTW should we make sure that this patch and the efi-bgrt patch get
> merged at the same time?

The 2 patches are related but merging them at the same time is not
necessary.

> I guess the net result is just that we get
> rid of some error in the log, but a rotated BMP will be ignored
> otherwise.

Right, worse case (if the bmp fits pre-rotation) it will be displayed
rotated. Note on the one machine I'm aware of which uses these bits
the bmp does not fit pre-rotation, so we end up triggering:

error:
         memunmap(bgrt_image);
         pr_warn("efifb: Ignoring BGRT: unexpected or invalid BMP data\n");
}

Which this patch replaces with hitting:

         if (bgrt_tab.status & 0x06) {
                 pr_info("efifb: BGRT rotation bits set, not showing boot graphics\n");
                 return;
         }

Instead. So at least on the one machine I know of this is 99% cosmetic.

> Or is it relevant for userland in some other way?

No.

Regards,

Hans