Hi Andy,
Thanks for the review.
On Wed, Apr 01, 2020 at 06:13:32PM +0300, Andy Shevchenko wrote:
On Wed, Apr 01, 2020 at 04:13:51PM +0200, Hans Verkuil wrote:
On 4/1/20 4:05 PM, Sakari Ailus wrote:
Add a printk modifier %ppf (for pixel format) for printing V4L2 and DRM pixel formats denoted by 4ccs. The 4cc encoding is the same for both so the same implementation can be used.
%p4cc ?
Sounds good. Numbers have special handling but AFAIR only right after % sign, so this should be possible.
- char ch[2] = { 0 };
This can just be '{ };'
The latter is GCC extension, while above is C standard. Former is slightly better I think. Though see below.
- unsigned int i;
- if (check_pointer(&buf, end, fourcc, spec))
return buf;- switch (fmt[1]) {
- case 'f':
for (i = 0; i < sizeof(*fourcc); i++) {ch[0] = *fourcc >> (i << 3);You need to AND with 0x7f, otherwise a big endian fourcc (bit 31 is set) will look wrong. Also, each character is standard 7 bit ascii, bit 7 isn't used except to indicate a BE variant.
Why not to do it once by a flag and do reset it once?
u32 tmp = *fourcc; bool be4cc = tmp & BIT(31);
tmp &= BIT(31);
I had two extra temporary variables in a version I didn't send but I figured they could be removed. :-)
On top of that, as promised above, why not simple do it in a simpler way, i.e. using standard idiom:
for (i = 0; i < sizeof(*fourcc); i++) { if (buf < end) *buf = tmp >> (i * 8); buf++; } ?
I guess that's at least more efficient, and comparing buf to end is trivial. I'll do that in v2.
buf = string(buf, end, ch, spec);}if (*fourcc & BIT(31))buf = string(buf, end, "-BE", spec);Another possibility
u8 ch[8];
if (*fourcc & BIT(31)) { put_unaligned_be32(tmp, &ch[0]); strcpy(&ch[4], "-BE"); } else { put_unaligned_le32(tmp, &ch[0]); strcpy(&ch[4], "-LE"); } return string(buf, end, &ch[0], spec);
I think I prefer the loop. I figured you can only call string once, otherwise field width handling will be broken. Let's see.
return buf;- default:
return error_string(buf, end, "(%pp?)", spec);- }
+}