Messages in this thread | | | Subject | Re: [PATCH] rtc: remove VLA usage | From | "Gustavo A. R. Silva" <> | Date | Wed, 7 Mar 2018 16:39:51 -0600 |
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Hi Alexandre,
On 03/07/2018 03:25 PM, Alexandre Belloni wrote: > On 07/03/2018 at 14:11:33 -0600, Gustavo A. R. Silva wrote: >> In preparation to enabling -Wvla, remove VLA and replace it >> with a fixed-length array instead. >> > You should probably explain what VLA is and why this is important to do.
Sure. I can elaborate a little bit more.
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> >> --- >> drivers/rtc/rtc-bq32k.c | 2 +- >> drivers/rtc/rtc-mcp795.c | 2 +- >> 2 files changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/rtc/rtc-bq32k.c b/drivers/rtc/rtc-bq32k.c >> index e8698e9..e4b234a 100644 >> --- a/drivers/rtc/rtc-bq32k.c >> +++ b/drivers/rtc/rtc-bq32k.c >> @@ -74,7 +74,7 @@ static int bq32k_read(struct device *dev, void *data, uint8_t off, uint8_t len) >> static int bq32k_write(struct device *dev, void *data, uint8_t off, uint8_t len) >> { >> struct i2c_client *client = to_i2c_client(dev); >> - uint8_t buffer[len + 1]; >> + uint8_t buffer[256]; >> > You chose to change len to 255, probably because this is a uint8_t but
Correct.
> this is way too much for this rtc, it only has 10 consecutive registers.
In that case probably the best solution is to add the following line to the module:
#define MAX_LEN 10
and update the rest of the code as follows:
uint8_t buffer[MAX_LEN + 1];
>> buffer[0] = off; >> memcpy(&buffer[1], data, len); >> diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c >> index 79e24ea..00e11c1 100644 >> --- a/drivers/rtc/rtc-mcp795.c >> +++ b/drivers/rtc/rtc-mcp795.c >> @@ -82,7 +82,7 @@ static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count) >> { >> struct spi_device *spi = to_spi_device(dev); >> int ret; >> - u8 tx[2 + count]; >> + u8 tx[257];
For this particular case it seems to me that the following works just fine:
#define MAX_COUNT 7
u8 tx[MAX_COUNT + 2];
What do you think?
Thanks for your feedback. -- Gustavo
>> >> tx[0] = MCP795_WRITE; >> tx[1] = addr; >> -- >> 2.7.4 >>
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