On Fri, 20 Sep 2024, Ville Syrjälä <[email protected]> wrote: > On Thu, Sep 12, 2024 at 03:15:52PM +0300, Jani Nikula wrote: >> On Tue, 10 Sep 2024, Ville Syrjala <[email protected]> wrote: >> > From: Ville Syrjälä <[email protected]> >> > >> > Replace the three hand rolled "$VBT"s with a vbt_signature[] >> > to avoid accidents. >> > >> > Signed-off-by: Ville Syrjälä <[email protected]> >> > --- >> > drivers/gpu/drm/i915/display/intel_bios.c | 12 +++++++++--- >> > 1 file changed, 9 insertions(+), 3 deletions(-) >> > >> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c >> > b/drivers/gpu/drm/i915/display/intel_bios.c >> > index cbbda94c3dab..0b92b494117f 100644 >> > --- a/drivers/gpu/drm/i915/display/intel_bios.c >> > +++ b/drivers/gpu/drm/i915/display/intel_bios.c >> > @@ -2964,6 +2964,8 @@ static const struct bdb_header *get_bdb_header(const >> > struct vbt_header *vbt) >> > return _vbt + vbt->bdb_offset; >> > } >> > >> > +static const char vbt_signature[4] = "$VBT"; >> >> Always a bit scary to add strings without termination, but I guess it's >> justified here. > > I guess we could make it look less like a string with eg. > static const u8 vbt_signature[] = { '$', 'V', 'B', 'T' }; > ?
Alternatively, static const char *vbt_signature = "$VBT"; > >> Reviewed-by: Jani Nikula <[email protected]> >> >> >> > + >> > /** >> > * intel_bios_is_valid_vbt - does the given buffer contain a valid VBT >> > * @display: display device >> > @@ -2986,7 +2988,7 @@ bool intel_bios_is_valid_vbt(struct intel_display >> > *display, >> > return false; >> > } >> > >> > - if (memcmp(vbt->signature, "$VBT", 4)) { >> > + if (memcmp(vbt->signature, vbt_signature, sizeof(vbt_signature))) { But then this would need strlen() >> > drm_dbg_kms(display->drm, "VBT invalid signature\n"); >> > return false; >> > } >> > @@ -3082,9 +3084,11 @@ static struct vbt_header *spi_oprom_get_vbt(struct >> > intel_display *display, >> > oprom_offset = intel_uncore_read(&i915->uncore, OROM_OFFSET); >> > oprom_offset &= OROM_OFFSET_MASK; >> > >> > + BUILD_BUG_ON(sizeof(vbt_signature) != sizeof(u32)); And maybe this could be sizeof(vbt_signature) < sizeof(u32) All of the alternatives are a bit disappointing, so maybe let's just roll with the patch you already have here? BR, Jani. >> > + >> > for (count = 0; count < oprom_size; count += 4) { >> > data = intel_spi_read32(&i915->uncore, oprom_offset + count); >> > - if (data == *((const u32 *)"$VBT")) { >> > + if (data == *((const u32 *)vbt_signature)) { >> > found = oprom_offset + count; >> > break; >> > } >> > @@ -3144,9 +3148,11 @@ static struct vbt_header *oprom_get_vbt(struct >> > intel_display *display, >> > if (!oprom) >> > return NULL; >> > >> > + BUILD_BUG_ON(sizeof(vbt_signature) != sizeof(u32)); >> > + >> > /* Scour memory looking for the VBT signature. */ >> > for (i = 0; i + 4 < size; i += 4) { >> > - if (ioread32(oprom + i) != *((const u32 *)"$VBT")) >> > + if (ioread32(oprom + i) != *((const u32 *)vbt_signature)) >> > continue; >> > >> > p = oprom + i; >> >> -- >> Jani Nikula, Intel -- Jani Nikula, Intel
