On Mon, Sep 23, 2024 at 12:12:39PM +0300, Jani Nikula wrote: > 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";
Or could just be something like: static const char vbt_signature[] = "$VBT"; static const int vbt_signature_len = 4; BUILD_BUG_ON(vbt_signature_len != sizeof(vbt_signature) - 1); BUILD_BUG_ON(vbt_signature_len != sizeof(u32)); and use vbt_signature_len instead sizeof(vbt_signature) everwhere. > > > > >> Reviewed-by: Jani Nikula <[email protected]> > >> > >> > >> > + > >> > /** > >> > * intel_bios_is_valid_vbt - does the given buffer contain a valid VBT > >> > * @display: display device > >> > @@ -2986,7 +2988,7 @@ bool intel_bios_is_valid_vbt(struct intel_display > >> > *display, > >> > return false; > >> > } > >> > > >> > - if (memcmp(vbt->signature, "$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 -- Ville Syrjälä Intel
