Messages in this thread Patch in this message | | | From | Frank Haverkamp <> | Subject | [RFC 1/2] CRC32 Add GenWQE CRC to kernel CRC code | Date | Wed, 11 Dec 2013 17:49:22 +0100 |
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Our GenWQE driver is using a CRC32 polynom, which as far as I could see, no one else is using in the kernel. In its original version we implemented our own CRC32, but I think it is nicer to use the common code as suggested by Greg.
I did not want to add yet another crc32g_table and waste (1KiB) memory when no one else is using it. I tried to externalize the crc32init_be_generic and crc32_be_generic functions. I failed. The crc32init* I found is used to autogenerate code can is itself not part of the resulting kernel.
As result I gave up on that approach and just added the GenWQE special polynom in addition to the other 3 crc tables. I wanted to figure out if it is possible in principle to use the generic code.
Is the consumption of 1KiB for a little table justifyable if it currently has just one user?
Signed-off-by: Frank Haverkamp <haver@linux.vnet.ibm.com> --- include/linux/crc32.h | 2 2 + 0 - 0 ! lib/crc32.c | 10 10 + 0 - 0 ! lib/crc32defs.h | 5 5 + 0 - 0 ! lib/gen_crc32table.c | 39 31 + 8 - 0 ! 4 files changed, 48 insertions(+), 8 deletions(-)
--- a/include/linux/crc32.h +++ b/include/linux/crc32.h @@ -11,6 +11,8 @@ extern u32 crc32_le(u32 crc, unsigned char const *p, size_t len); extern u32 crc32_be(u32 crc, unsigned char const *p, size_t len); +extern u32 __crc32g_be(u32 crc, unsigned char const *p, size_t len); + /** * crc32_le_combine - Combine two crc32 check values into one. For two * sequences of bytes, seq1 and seq2 with lengths len1 --- a/lib/crc32.c +++ b/lib/crc32.c @@ -339,14 +339,24 @@ u32 __pure crc32_be(u32 crc, unsigned ch { return crc32_be_generic(crc, p, len, NULL, CRCPOLY_BE); } +u32 __pure __crc32g_be(u32 crc, unsigned char const *p, size_t len) +{ + return crc32_be_generic(crc, p, len, NULL, CRC32G_POLY_BE); +} #else u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) { return crc32_be_generic(crc, p, len, (const u32 (*)[256])crc32table_be, CRCPOLY_BE); } +u32 __pure __crc32g_be(u32 crc, unsigned char const *p, size_t len) +{ + return crc32_be_generic(crc, p, len, + (const u32 (*)[256])crc32gtable_be, CRC32G_POLY_BE); +} #endif EXPORT_SYMBOL(crc32_be); +EXPORT_SYMBOL(__crc32g_be); #ifdef CONFIG_CRC32_SELFTEST --- a/lib/crc32defs.h +++ b/lib/crc32defs.h @@ -13,6 +13,11 @@ */ #define CRC32C_POLY_LE 0x82F63B78 +/* + * This is the CRC32g polynomial, used by the GenWQE driver. + */ +#define CRC32G_POLY_BE 0x20044009 + /* Try to choose an implementation variant via Kconfig */ #ifdef CONFIG_CRC32_SLICEBY8 # define CRC_LE_BITS 64 --- a/lib/gen_crc32table.c +++ b/lib/gen_crc32table.c @@ -24,6 +24,7 @@ static uint32_t crc32table_le[LE_TABLE_ROWS][256]; static uint32_t crc32table_be[BE_TABLE_ROWS][256]; static uint32_t crc32ctable_le[LE_TABLE_ROWS][256]; +static uint32_t crc32gtable_be[BE_TABLE_ROWS][256]; /** * crc32init_le() - allocate and initialize LE table data @@ -65,29 +66,40 @@ static void crc32cinit_le(void) } /** - * crc32init_be() - allocate and initialize BE table data + * crc32init_be_generic() - allocate and initialize BE table data */ -static void crc32init_be(void) +static void crc32init_be_generic(const uint32_t polynomial, + uint32_t (*tab)[256]) { unsigned i, j; uint32_t crc = 0x80000000; - crc32table_be[0][0] = 0; + tab[0][0] = 0; for (i = 1; i < BE_TABLE_SIZE; i <<= 1) { - crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0); + crc = (crc << 1) ^ ((crc & 0x80000000) ? polynomial : 0); for (j = 0; j < i; j++) - crc32table_be[0][i + j] = crc ^ crc32table_be[0][j]; + tab[0][i + j] = crc ^ tab[0][j]; } for (i = 0; i < BE_TABLE_SIZE; i++) { - crc = crc32table_be[0][i]; + crc = tab[0][i]; for (j = 1; j < BE_TABLE_ROWS; j++) { - crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8); - crc32table_be[j][i] = crc; + crc = tab[0][(crc >> 24) & 0xff] ^ (crc << 8); + tab[j][i] = crc; } } } +static void crc32init_be(void) +{ + crc32init_be_generic(CRCPOLY_BE, crc32table_be); +} + +static void crc32ginit_be(void) +{ + crc32init_be_generic(CRC32G_POLY_BE, crc32gtable_be); +} + static void output_table(uint32_t (*table)[256], int rows, int len, char *trans) { int i, j; @@ -126,6 +138,7 @@ int main(int argc, char** argv) BE_TABLE_SIZE, "tobe"); printf("};\n"); } + if (CRC_LE_BITS > 1) { crc32cinit_le(); printf("static u32 __cacheline_aligned " @@ -136,5 +149,15 @@ int main(int argc, char** argv) printf("};\n"); } + if (CRC_BE_BITS > 1) { + crc32ginit_be(); + printf("static u32 __cacheline_aligned " + "crc32gtable_be[%d][%d] = {", + BE_TABLE_ROWS, BE_TABLE_SIZE); + output_table(crc32gtable_be, LE_TABLE_ROWS, + BE_TABLE_SIZE, "tobe"); + printf("};\n"); + } + return 0; }
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