[Letux-kernel] [PATCH v3 2/4] gpio: pca953x: add register definitions for pcal6524 and fix address calculation

H. Nikolaus Schaller hns at goldelico.com
Wed Apr 25 20:05:36 CEST 2018

Hi Andy,

> Am 11.04.2018 um 07:00 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> Hi Andy,
>> Am 10.04.2018 um 20:06 schrieb Andy Shevchenko <andy.shevchenko at gmail.com>:
>> On Tue, Apr 10, 2018 at 7:07 PM, H. Nikolaus Schaller <hns at goldelico.com> wrote:
>>> PCAL chips ("L" seems to stand for "latched") have additional
>>> registers starting at address 0x40 to control the latches,
>>> interrupt mask, pull-up and pull down etc.
>>> The constants are so far defined in a way that they fit for
>>> the pcal9555a when shifted by the number of banks, i.e. multiplied
>>> by 2.
>>> Now the pcal6524 has 3 banks which means the relative offset
>>> must be multiplied by 4 which gives a wrong result if not done
>>> carefully, since the base offset is already included in the offset.
>>> For the basic registers shared with all pca93xx/tca64xx chips
>>> there is no such offset.
>>> Therefore, we add code to adjust the register number for exended
>>> registers to the 24 bit accessor functions.
>>> And we add additional register offset constants (not yet used by
>>> the driver code) which are specific to the pcal6524.
>> First of all, as I said, please split this to two patches. Don't mix the things.
> Ok. Queued for v4.
>>> +       /* adjust register address for pcal6524 */
>>> +       if (reg >= PCAL953X_OUT_STRENGTH)
>>> +               reg -= PCAL953X_OUT_STRENGTH >> 1;
>>> +
>> Give me some days to think about it.

Any news on this?

I am waiting for your advice before submitting v4 (with pending updates for the other patches).

> No problem. I'll wait with v4.
> The only alternative I would see is to add new accessor function
> pointers for the extended registers and have 0x00 based offsets,
> but that is IMHO more ugly.
> BR and thanks,
> Nikolaus

BR and thanks,

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