Hi, 2018-03-13 0:31 GMT+01:00 Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>: > Hi, > > On 13/03/2018 at 00:13:38 +0100, Stefano Manni wrote: >> In preparation to enabling -Wvla, remove VLAs and replace them with >> fixed-length arrays instead. >> >> rtc-mcp795.c uses a variable-length array declaration to contain >> the command to write the rtcc; this can be replaced by a fixed- >> size array of length 2 (instruction, address) + 32 (data out), >> assuming a maximum data length of 32 bytes before wrap up. >> >> This was prompted by https://lkml.org/lkml/2018/3/7/621 >> >> Signed-off-by: Stefano Manni <stefano.manni@xxxxxxxxx> >> --- >> drivers/rtc/rtc-mcp795.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c >> index 77f21331ae21..a5f504e2364c 100644 >> --- a/drivers/rtc/rtc-mcp795.c >> +++ b/drivers/rtc/rtc-mcp795.c >> @@ -61,6 +61,9 @@ >> >> #define SEC_PER_DAY (24 * 60 * 60) >> >> +/* Maximum length for data out in write operation to RTCC */ >> +#define MCP795_MAX_DATAOUT_LEN 32 >> + > > This is wrong, see https://marc.info/?l=linux-kernel&m=152046370320811&w=2 > > Also, https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git/commit/?h=rtc-next&id=74ce1a932504da166cfbccf5567aa3751b6aa599 > You sure that the right value to use is 255 + 2? mcp795_rtcc_write() just writes into the RTCC that contains only 32 registers (table 4-1 of datasheet). I assumed 32 as the maximum length of data to write before wrapping up (start from reg 0x0). Probably 32 is just a wrong assumption but why did you choose 255? Another thing: don't we need also to check count against the array length? if (count > MCP795_MAX_DATAOUT_LEN) return -EINVAL;
