[PATCH] rtc: remove VLA usage

[PATCH] rtc: remove VLA usage

[Gustavo A. R. Silva]

In preparation to enabling -Wvla, remove VLA and replace it
with a fixed-length array instead.

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];
 
 	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];
 
 	tx[0] = MCP795_WRITE;
 	tx[1] = addr;
-- 
2.7.4

Re: [PATCH] rtc: remove VLA usage

[Alexandre Belloni]

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.

> 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
this is way too much for this rtc, it only has 10 consecutive registers.

>  	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];
>  
>  	tx[0] = MCP795_WRITE;
>  	tx[1] = addr;
> -- 
> 2.7.4
> 

-- 
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] rtc: remove VLA usage

[Gustavo A. R. Silva]

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
>>

Re: [PATCH] rtc: remove VLA usage

[Gustavo A. R. Silva]

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
>>

Re: [PATCH] rtc: remove VLA usage

[Alexandre Belloni]

On 07/03/2018 at 16:39:51 -0600, Gustavo A. R. Silva wrote:
> 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];
> 

Seems better, yes.

> 
> > >   	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?
> 

Nope, that RTC has a section of 255 bytes that could be read at once so
257 is the correct value.


-- 
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] rtc: remove VLA usage

[Gustavo A. R. Silva]

On 03/07/2018 05:01 PM, Alexandre Belloni wrote:
> On 07/03/2018 at 16:39:51 -0600, Gustavo A. R. Silva wrote:
>> 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];
>>
> Seems better, yes.
>
>>>>    	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?
>>
> Nope, that RTC has a section of 255 bytes that could be read at once so
> 257 is the correct value.
>

I see...

I was looking into this piece of code drivers/rtc/rtc-mcp795.c:302:

         tmp[0] = (tmp[0] & 0x80) | bin2bcd(alm->time.tm_sec);
         tmp[1] = (tmp[1] & 0x80) | bin2bcd(alm->time.tm_min);
         tmp[2] = (tmp[2] & 0xE0) | bin2bcd(alm->time.tm_hour);
         tmp[3] = (tmp[3] & 0x80) | bin2bcd(alm->time.tm_wday + 1);
         /* set alarm match: seconds, minutes, hour, day, date and month */
         tmp[3] |= (MCP795_ALM0C2_BIT | MCP795_ALM0C1_BIT | 
MCP795_ALM0C0_BIT);
         tmp[4] = (tmp[4] & 0xC0) | bin2bcd(alm->time.tm_mday);
         tmp[5] = (tmp[5] & 0xE0) | bin2bcd(alm->time.tm_mon + 1);

         ret = mcp795_rtcc_write(dev, MCP795_REG_ALM0_SECONDS, tmp, 
sizeof(tmp));


OK. I'll work on v2 of this patch. I'll send it shortly.

Thanks
--
Gustavo

Re: [PATCH] rtc: remove VLA usage

[Alexandre Belloni]

On 07/03/2018 at 17:09:22 -0600, Gustavo A. R. Silva wrote:
> 
> 
> On 03/07/2018 05:01 PM, Alexandre Belloni wrote:
> > On 07/03/2018 at 16:39:51 -0600, Gustavo A. R. Silva wrote:
> > > 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];
> > > 
> > Seems better, yes.
> > 
> > > > >    	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?
> > > 
> > Nope, that RTC has a section of 255 bytes that could be read at once so
> > 257 is the correct value.
> > 
> 
> I see...
> 
> I was looking into this piece of code drivers/rtc/rtc-mcp795.c:302:
> 
>         tmp[0] = (tmp[0] & 0x80) | bin2bcd(alm->time.tm_sec);
>         tmp[1] = (tmp[1] & 0x80) | bin2bcd(alm->time.tm_min);
>         tmp[2] = (tmp[2] & 0xE0) | bin2bcd(alm->time.tm_hour);
>         tmp[3] = (tmp[3] & 0x80) | bin2bcd(alm->time.tm_wday + 1);
>         /* set alarm match: seconds, minutes, hour, day, date and month */
>         tmp[3] |= (MCP795_ALM0C2_BIT | MCP795_ALM0C1_BIT |
> MCP795_ALM0C0_BIT);
>         tmp[4] = (tmp[4] & 0xC0) | bin2bcd(alm->time.tm_mday);
>         tmp[5] = (tmp[5] & 0xE0) | bin2bcd(alm->time.tm_mon + 1);
> 
>         ret = mcp795_rtcc_write(dev, MCP795_REG_ALM0_SECONDS, tmp,
> sizeof(tmp));
> 

Yeah, the 128 or 255 bytes NVRAM is not yet supported but this is on my
todo list

-- 
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] rtc: remove VLA usage

[Gustavo A. R. Silva]

On 03/07/2018 05:12 PM, Alexandre Belloni wrote:
> On 07/03/2018 at 17:09:22 -0600, Gustavo A. R. Silva wrote:
>>
>> On 03/07/2018 05:01 PM, Alexandre Belloni wrote:
>>> On 07/03/2018 at 16:39:51 -0600, Gustavo A. R. Silva wrote:
>>>> 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];
>>>>
>>> Seems better, yes.
>>>
>>>>>>     	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?
>>>>
>>> Nope, that RTC has a section of 255 bytes that could be read at once so
>>> 257 is the correct value.
>>>
>> I see...
>>
>> I was looking into this piece of code drivers/rtc/rtc-mcp795.c:302:
>>
>>          tmp[0] = (tmp[0] & 0x80) | bin2bcd(alm->time.tm_sec);
>>          tmp[1] = (tmp[1] & 0x80) | bin2bcd(alm->time.tm_min);
>>          tmp[2] = (tmp[2] & 0xE0) | bin2bcd(alm->time.tm_hour);
>>          tmp[3] = (tmp[3] & 0x80) | bin2bcd(alm->time.tm_wday + 1);
>>          /* set alarm match: seconds, minutes, hour, day, date and month */
>>          tmp[3] |= (MCP795_ALM0C2_BIT | MCP795_ALM0C1_BIT |
>> MCP795_ALM0C0_BIT);
>>          tmp[4] = (tmp[4] & 0xC0) | bin2bcd(alm->time.tm_mday);
>>          tmp[5] = (tmp[5] & 0xE0) | bin2bcd(alm->time.tm_mon + 1);
>>
>>          ret = mcp795_rtcc_write(dev, MCP795_REG_ALM0_SECONDS, tmp,
>> sizeof(tmp));
>>
> Yeah, the 128 or 255 bytes NVRAM is not yet supported but this is on my
> todo list
>

I got it.

Thanks
--
Gustavo