> On 20 Feb 2025, at 10:09 PM, Aditya Garg <gargaditya08@xxxxxxxx> wrote: > > From: Hector Martin <marcan@xxxxxxxxx> > > %p4cc is designed for DRM/V4L2 FOURCCs with their specific quirks, but > it's useful to be able to print generic 4-character codes formatted as > an integer. Extend it to add format specifiers for printing generic > 32-bit FOURCCs with various endian semantics: > > %p4ch Host-endian > %p4cl Little-endian > %p4cb Big-endian > %p4cr Reverse-endian > > The endianness determines how bytes are interpreted as a u32, and the > FOURCC is then always printed MSByte-first (this is the opposite of > V4L/DRM FOURCCs). This covers most practical cases, e.g. %p4cr would > allow printing LSByte-first FOURCCs stored in host endian order > (other than the hex form being in character order, not the integer > value). > > Signed-off-by: Hector Martin <marcan@xxxxxxxxx> > Signed-off-by: Aditya Garg <gargaditya08@xxxxxxxx> BTW, after looking at the comments by Martin [1], its actually better to use existing specifiers for the appletbdrm driver. The driver needs the host endian as proposed by this patch, so instead of that, we can use %.4s [1]: https://lore.kernel.org/asahi/E753B391-D2CB-4213-AF82-678ADD5A7644@xxxxxxxxxxx/ Alternatively we could add a host endian only. Other endians are not really used by any driver AFAIK. The host endian is being used by appletbdrm and Asahi Linux’ SMC driver only. > > > --- > - *p++ = ' '; > - strcpy(p, orig & BIT(31) ? "big-endian" : "little-endian"); > - p += strlen(p); > + if (pixel_fmt) { > + *p++ = ' '; > + strcpy(p, orig & BIT(31) ? "big-endian" : "little-endian"); > + p += strlen(p); > + }
