[PATCH 1/1] lib/vsprintf: Add support for printing V4L2 and DRM fourccs

Sakari Ailus
2020-04-01T14:05:26Z

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.
+
+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 };
+ 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);
+ 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.
* - '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':
--
2.20.1