Re: [PATCH v6 1/3] spi/pl022: Add chip select handling via GPIO

[shiraz hashim <shiraz.linux.kernel@gmail.com>]

Hi Linus,

On Sun, Sep 2, 2012 at 12:48 PM, Linus Walleij <linus.walleij@linaro.org> wrote:
> On Sat, Sep 1, 2012 at 1:14 PM, shiraz hashim
> <shiraz.linux.kernel@gmail.com> wrote:
>> Hi Roland,
>>
>> On Wed, Aug 22, 2012 at 7:19 PM, Roland Stigge <stigge@antcom.de> wrote:
>>> @@ -2016,6 +2030,8 @@ pl022_probe(struct amba_device *adev, co
>>>         pl022->master_info = platform_info;
>>>         pl022->adev = adev;
>>>         pl022->vendor = id->data;
>>> +       /* Point chipselects to allocated memory beyond the main struct */
>>> +       pl022->chipselects = (int *) pl022 + sizeof(struct pl022);
>>
>> This is going beyond memory allocated for chipselects
>> as it adds 4 * sizeof(struct pl022) bytes to pl022.
>
> Yes that is why the allocation looks like this:
>
> +       master = spi_alloc_master(dev, sizeof(struct pl022) + sizeof(int) *
> +                                 platform_info->num_chipselect);
>

The allocation is such because type of chipselects is int.

The statement for allocation is correct, but

       pl022->chipselects = (int *) pl022 + sizeof(struct pl022);

is not adding  sizeof(struct pl022) bytes to pl022 base (which we want),
but infact 4 times the size of pl022 (because type of pl022 is now int *).

Do you get my point ?  This would go way beyond memory allocated
for chipselects.

-- 
regards
Shiraz Hashim