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.

Suggested-by: Mauro Carvalho Chehab mchehab@kernel.org Signed-off-by: Sakari Ailus sakari.ailus@linux.intel.com

---

Documentation/core-api/printk-formats.rst | 11 +++++++++ lib/vsprintf.c | 29 +++++++++++++++++++++++ 2 files changed, 40 insertions(+)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 8ebe46b1af39..b6249f513c09 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -545,6 +545,17 @@ For printing netdev_features_t.

Passed by reference.

+V4L2 and DRM fourcc code (pixel format) +---------------------------------------

+::

• %ppf

+Print a 4cc code used by V4L2 or DRM.

FourCC appears to be the more-or-less official name (https://en.wikipedia.org/wiki/FourCC)

I would explain about the -BE suffix for bigendian fourcc variants.

+Passed by reference.

Thanks

diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 7c488a1ce318..b39f0ac317c5 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -1721,6 +1721,32 @@ char *netdev_bits(char *buf, char *end, const void *addr, return special_hex_number(buf, end, num, size); }

+static noinline_for_stack +char *pixel_format_string(char *buf, char *end, const u32 *fourcc,

• 	  struct printf_spec spec, const char *fmt)
  

+{

• char ch[2] = { 0 };

This can just be '{ };'

• 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.

• 	buf = string(buf, end, ch, spec);
  

• }
  

• if (*fourcc & BIT(31))
  

• 	buf = string(buf, end, "-BE", spec);
  

• return buf;
  

• default:

• return error_string(buf, end, "(%pp?)", spec);
  

• }

+}

static noinline_for_stack char *address_val(char *buf, char *end, const void *addr, struct printf_spec spec, const char *fmt) @@ -2131,6 +2157,7 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,

•   correctness of the format string and va_list arguments.
  

• • 'K' For a kernel pointer that should be hidden from unprivileged users
• • 'NF' For a netdev_features_t

• • • 'pf' V4L2 or DRM pixel format.

I'd say 'FourCC format' instead of 'pixel format'.

• • 'h[CDN]' For a variable-length buffer, it prints it as a hex string with

•        a certain separator (' ' by default):
  

•          C colon
  

@@ -2223,6 +2250,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, return restricted_pointer(buf, end, ptr, spec); case 'N': return netdev_bits(buf, end, ptr, spec, fmt);

• case 'p':

• return pixel_format_string(buf, end, ptr, spec, fmt);
  

  case 'a': return address_val(buf, end, ptr, spec, fmt); case 'd':

Regards,

Hans