[PATCH v2] drm/bochs: add edid present check

[Daniel Vetter]

On Thu, Dec 20, 2018 at 07:50:01AM +0100, Gerd Hoffmann wrote:
> Check first two header bytes before trying to read the edid blob,
> to avoid the log being spammed in case qemu has no edid support (old
> qemu or edid turned off).
> 
> Fixes: 01f23459cf drm/bochs: add edid support.
> Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>

It's a bit a hack, but makes sense.

Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> ---
>  drivers/gpu/drm/bochs/bochs_hw.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bochs/bochs_hw.c b/drivers/gpu/drm/bochs/bochs_hw.c
> index c90a0d492f..e1f8ffce00 100644
> --- a/drivers/gpu/drm/bochs/bochs_hw.c
> +++ b/drivers/gpu/drm/bochs/bochs_hw.c
> @@ -89,6 +89,14 @@ int bochs_hw_load_edid(struct bochs_device *bochs)
>  	if (!bochs->mmio)
>  		return -1;
>  
> +	/*
> +	 * Check first two EDID blob header bytes to figure whenever
> +	 * edid support is enabled in qemu.
> +	 */
> +	if (readb(bochs->mmio + 0) != 0x00 ||
> +	    readb(bochs->mmio + 1) != 0xff)
> +		return -1;
> +
>  	kfree(bochs->edid);
>  	bochs->edid = drm_do_get_edid(&bochs->connector,
>  				      bochs_get_edid_block, bochs);
> -- 
> 2.9.3
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch