[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 11 07:00:04 CEST 2018

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.

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,

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