Re: [PATCH 3/3] drm/i915/bios: assume vbt is 4-byte aligned into oprom

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 26 Nov 2019, Lucas De Marchi <lucas.demarchi@intel.com> wrote:
> The unaligned ioread32() will make us read byte by byte looking for the
> vbt. We could just as well have done a ioread8() + a shift and avoid the
> extra confusion on how we are looking for "$VBT".
>
> However when using ACPI it's guaranteed the VBT is 4-byte aligned
> per spec, so we can probably assume it here as well.
>
> v2: do not try to simplify the loop by eliminating the auxiliary counter
> (Jani and Ville)
>
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


> ---
>  drivers/gpu/drm/i915/display/intel_bios.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index 56e566945e98..fec6752b1f56 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -1909,7 +1909,7 @@ static struct vbt_header *oprom_get_vbt(struct drm_i915_private *dev_priv)
>  		return NULL;
>  
>  	/* Scour memory looking for the VBT signature. */
> -	for (i = 0; i + 4 < size; i++) {
> +	for (i = 0; i + 4 < size; i += 4) {
>  		if (ioread32(oprom + i) != *((const u32 *)"$VBT"))
>  			continue;

-- 
Jani Nikula, Intel Open Source Graphics Center
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