Add a printk modifier %p4cc (for pixel format) for printing V4L2 and DRM pixel formats denoted by fourccs. The fourcc 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 --- since v2:
- Add comments to explain why things are being done
- Print characters under 32 (space) as hexadecimals in parenthesis.
- Do not print spaces in the fourcc codes.
- Make use of a loop over the fourcc characters instead of put_unaligned_le32(). This is necessary to omit spaces in the output.
- Use DRM style format instead of V4L2. This provides the precise code as a numerical value as well as explicit endianness information.
- Added WARN_ON_ONCE() sanity checks. Comments on these are welcome; I'd expect them mostly be covered by the tests.
- Added tests for %p4cc in lib/test_printf.c
Documentation/core-api/printk-formats.rst | 12 ++++ lib/test_printf.c | 17 +++++ lib/vsprintf.c | 86 +++++++++++++++++++++++ 3 files changed, 115 insertions(+)
diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 8ebe46b1af39..7aa0451e06fb 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -545,6 +545,18 @@ For printing netdev_features_t.
Passed by reference.
+V4L2 and DRM FourCC code (pixel format) +--------------------------------------- + +:: + + %p4cc + +Print a FourCC code used by V4L2 or DRM, including format endianness and +its numerical value as hexadecimal. + +Passed by reference. + Thanks ======
diff --git a/lib/test_printf.c b/lib/test_printf.c index 2d9f520d2f27..a14754086707 100644 --- a/lib/test_printf.c +++ b/lib/test_printf.c @@ -624,6 +624,22 @@ static void __init fwnode_pointer(void) software_node_unregister_nodes(softnodes); }
+static void __init fourcc_pointer(void) +{ + struct { + u32 code; + char *str; + } const try[] = { + { 0x20104646, "FF(10) little-endian (0x20104646)", }, + { 0xa0104646, "FF(10) big-endian (0xa0104646)", }, + { 0x10111213, "(13)(12)(11)(10) little-endian (0x10111213)", }, + }; + unsigned int i; + + for (i = 0; i < ARRAY_SIZE(try); i++) + test(try[i].str, "%p4cc", &try[i].code); +} + static void __init errptr(void) { @@ -668,6 +684,7 @@ test_pointer(void) flags(); errptr(); fwnode_pointer(); + fourcc_pointer(); }
static void __init selftest(void) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 7c488a1ce318..02e7906619c0 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -1721,6 +1721,89 @@ char *netdev_bits(char *buf, char *end, const void *addr, return special_hex_number(buf, end, num, size); }
+static noinline_for_stack +char *fourcc_string(char *buf, char *end, const u32 *__fourcc, + struct printf_spec spec, const char *fmt) +{ +#define FOURCC_HEX_CHAR_STR "(xx)" +#define FOURCC_BIG_ENDIAN_STR " big-endian" +#define FOURCC_LITTLE_ENDIAN_STR " little-endian" +#define FOURCC_HEX_NUMBER " (0x01234567)" +#define FOURCC_STRING_MAX \ + FOURCC_HEX_CHAR_STR FOURCC_HEX_CHAR_STR FOURCC_HEX_CHAR_STR \ + FOURCC_HEX_CHAR_STR FOURCC_LITTLE_ENDIAN_STR FOURCC_HEX_NUMBER + struct printf_spec my_spec = { + .type = FORMAT_TYPE_UINT, + .field_width = 2, + .flags = SMALL, + .base = 16, + .precision = -1, + }; + char __s[sizeof(FOURCC_STRING_MAX)]; + char *s = __s; + unsigned int i; + /* + * The 31st bit defines the endianness of the data, so save its printing + * for later. + */ + u32 fourcc = *__fourcc & ~BIT(31); + int ret; + + if (check_pointer(&buf, end, __fourcc, spec)) + return buf; + + if (fmt[1] != 'c' || fmt[2] != 'c') + return error_string(buf, end, "(%p4?)", spec); + + for (i = 0; i < sizeof(fourcc); i++, fourcc >>= 8) { + unsigned char c = fourcc; + + /* Weed out spaces */ + if (c == ' ') + continue; + + /* Print non-control characters as-is */ + if (c > ' ') { + *s = c; + s++; + continue; + } + + if (WARN_ON_ONCE(sizeof(__s) < + (s - __s) + sizeof(FOURCC_HEX_CHAR_STR))) + break; + + *s = '('; + s++; + s = number(s, s + 2, c, my_spec); + *s = ')'; + s++; + } + + ret = strscpy(s, *__fourcc & BIT(31) ? FOURCC_BIG_ENDIAN_STR + : FOURCC_LITTLE_ENDIAN_STR, + sizeof(__s) - (s - __s)); + if (!WARN_ON_ONCE(ret < 0)) + s += ret; + + if (!WARN_ON_ONCE(sizeof(__s) < + (s - __s) + sizeof(FOURCC_HEX_NUMBER))) { + *s = ' '; + s++; + *s = '('; + s++; + /* subtract parentheses and the space from the size */ + special_hex_number(s, s + sizeof(FOURCC_HEX_NUMBER) - 3, + *__fourcc, sizeof(u32)); + s += sizeof(u32) * 2 + 2 /* 0x */; + *s = ')'; + s++; + *s = '\0'; + } + + return string(buf, end, __s, spec); +} + static noinline_for_stack char *address_val(char *buf, char *end, const void *addr, struct printf_spec spec, const char *fmt) @@ -2131,6 +2214,7 @@ 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 + * - '4cc' V4L2 or DRM FourCC code, with endianness and raw numerical value. * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with * a certain separator (' ' by default): * C colon @@ -2223,6 +2307,8 @@ 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 '4': + return fourcc_string(buf, end, ptr, spec, fmt); case 'a': return address_val(buf, end, ptr, spec, fmt); case 'd':