Messages in this thread | | | Subject | Re: [RESEND PATCH v3 1/1] lib/vsprintf: Add support for printing V4L2 and DRM fourccs | From | Joe Perches <> | Date | Mon, 27 Apr 2020 09:02:34 -0700 |
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On Mon, 2020-04-27 at 17:53 +0300, Sakari Ailus wrote: > 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. [] > - Added WARN_ON_ONCE() sanity checks. Comments on these are welcome; I'd > expect them mostly be covered by the tests.
All the WARN_ON_ONCE uses are not necessary.
> diff --git 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)
There's no reason to use __ prefixed argument names here.
> +{ > +#define FOURCC_HEX_CHAR_STR "(xx)" > +#define FOURCC_BIG_ENDIAN_STR " big-endian" > +#define FOURCC_LITTLE_ENDIAN_STR " little-endian"
I don't believe used-once macro defines are useful.
> +#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
This is very difficult to read and is size dependent on the size of little-endian > big_endian
I'd write it out
FOURCC_STRING_MAX sizeof("(xx)(xx)(xx)(xx) little-endian (0x01234567)")
and then not have the define at all but use the written out string in the declaration.
> + struct printf_spec my_spec = { > + .type = FORMAT_TYPE_UINT, > + .field_width = 2, > + .flags = SMALL, > + .base = 16, > + .precision = -1, > + };
my_spec isn't usefully named, likely not necessary at all, and if really necessary, it should be static const
> + char __s[sizeof(FOURCC_STRING_MAX)];
I'd declare the buffer
char fourcc[sizeof("(xx)(xx)(xx)(xx) little-endian (0x01234567)"];
like all the other specialty functions do.
> + char *s = __s;
There's no reason to use __ prefixed variable names here either. All the other specialty function use:
char *p = <output_buffer_name>;
> + unsigned int i;
just int i; is typical
> + /* > + * The 31st bit defines the endianness of the data, so save its printing > + * for later. > + */ > + u32 fourcc = *__fourcc & ~BIT(31);
bool be = 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 >> (i*8);
Please remove the fourcc >>= 8 from the loop and use
unsigned char c = fourcc >> (i*8);
If I understand this correctly, I think this is simpler:
if (isascii(c) && isprint(c)) { *s++ = c; } else { *s++ = '('; s = hex_byte_pack(s, c); *s++ = ')'; }
> + > + /* 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 you size the initial buffer correctly, strscpy is unnecessary.
strcpy(s, <bit31> ? "big endian" : "little endian"); s += strlen(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++;
*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++ = ')';
> + *s = '\0'; > + } > + > + return string(buf, end, __s, spec); > +} >
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