On Thu, Nov 21, 2019 at 03:09:03PM +0200, Jani Nikula wrote:
On Wed, 20 Nov 2019, Lucas De Marchi <lucas.demar...@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 "$VBT".
However when using ACPI it's guaranteed the VBT is 4-byte aligned
per spec, so we can probably assume it here as well.
Signed-off-by: Lucas De Marchi <lucas.demar...@intel.com>
---
drivers/gpu/drm/i915/display/intel_bios.c | 19 ++++++-------------
1 file changed, 6 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_bios.c
b/drivers/gpu/drm/i915/display/intel_bios.c
index aa9b182efee5..6bf57b1ad056 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -1902,27 +1902,20 @@ static struct vbt_header *oprom_get_vbt(struct
drm_i915_private *dev_priv)
void __iomem *p = NULL, *oprom;
struct vbt_header *vbt;
u16 vbt_size;
- size_t i, size;
+ size_t size;
oprom = pci_map_rom(pdev, &size);
if (!oprom)
return NULL;
/* Scour memory looking for the VBT signature. */
- for (i = 0; i + 4 < size; i++) {
- if (ioread32(oprom + i) != *((const u32 *)"$VBT"))
- continue;
-
- p = oprom + i;
- size -= i;
- break;
- }
-
- if (!p)
- goto err_unmap_oprom;
+ for (p = oprom; size >= 4; p += 4, size -= 4)
+ if (ioread32(p) == *((const u32 *)"$VBT"))
+ break;
I think the original is easier to read. You only really need to change
"i++" to "i += 4" and be done with it.
I really liked this version much more... shorter and with only one control
variable rather than keeping the control in 3 different places (i, size
and p).
Lucas De Marchi
BR,
Jani.
if (sizeof(struct vbt_header) > size) {
- DRM_DEBUG_DRIVER("VBT header incomplete\n");
+ if (size >= 4)
+ DRM_DEBUG_DRIVER("VBT header incomplete\n");
goto err_unmap_oprom;
}
--
Jani Nikula, Intel Open Source Graphics Center
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
