On 06/19/2011 03:44 PM, Gilles Chanteperdrix wrote:
> On 06/19/2011 03:34 PM, Andrey Nechypurenko wrote:
>> Hi Gilles,
>>
>>>> fd = open("/dev/mem", O_RDWR | O_SYNC);
>>>> i2c_base = mmap(NULL, sizeof(i2c_base),
>>>> PROT_READ | PROT_WRITE,
>>>> MAP_SHARED, fd, I2C_DEFAULT_BASE);
>>>
>>> What is the value of i2c_base here? If it is MAP_FAILED, then mmap
>>> failed. And one reason for failing would be that sizeof(i2c_base) is not
>>> a multiple of the page size.
>>
>> In actual code I do check for the errors like below and it seams like
>> memory is mapped without errors:
>>
>> if(i2c_base == NULL)
>> {
>> fd = open("/dev/mem", O_RDWR | O_SYNC);
>> if(fd < 0)
>> {
>> fprintf(stderr, "Could not open memory\n");
>> return;
>> }
>>
>> i2c_base =
>> (volatile struct i2c *)mmap(NULL, sizeof(i2c_base),
>> PROT_READ | PROT_WRITE,
>> MAP_SHARED, fd, I2C_DEFAULT_BASE);
>> if(i2c_base == MAP_FAILED)
>> {
>> fprintf(stderr, "Memory Mapping failed\n");
>> close(fd);
>> return;
>> }
>> }
>>
>> Regarding the size of the memory mapped block - i2c_base is a pointer
>> and that is why, the mmap invocation above is incorrect. It should be
>> mmap(NULL, sizeof(struct i2c). This is a typo resulted by multiple
>> experiments I was doing. sizeof(struct i2c) is 64 and event with this
>> value, the same "Bus error" message is printed and the application
>> quits.
>
> Ok. I would pass the size of an entire page anyway, I do not think
> mapping anything not aligned on a page boundary makes sense.
>
> If it still fails, enable CONFIG_DEBUG_USER in kernel configuration,
> pass user_debug=29 on kernel command line, and post the user debug log
> upon failure, then the disassembly of the function where the SIGBUS happens.
>
> Note that this mailing list is probably not the best place to ask your
> question, since we mostly talk about Xenomai here, and your issue does
> not seem to have anything to do with Xenomai.
>
> Please keep the discussion public.
Second stupid questions: are you sure all the clocks needed to get that
I2C module running are enabled?
--
Gilles.
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