Re: [PATCH] pinctrl: mcp23s08: Initialize mcp->dev and mcp->addr before regmap init

[Judith Mendez <jm@ti.com>]

Hi Linus,

On 5/11/26 4:13 AM, Linus Walleij wrote:
> Hi Judith,
> 
> thanks for your patch!
> 
> On Fri, May 8, 2026 at 11:43 PM Judith Mendez <jm@ti.com> wrote:
> 
>> Regmap initialization triggers regcache_maple_populate() which attempts
>> SPI read to populate cache. SPI read requires mcp->dev and mcp->addr to
>> be set, without them, NULL pointer dereference occurs during probe.
>>
>> Move initialization before mcp23s08_spi_regmap_init() call.
>>
>> Cc: stable@vger.kernel.org
>> Fixes: f9f4fda15e72 ("pinctrl: mcp23s08: init reg_defaults from HW at probe and switch cache type")
>> Signed-off-by: Judith Mendez <jm@ti.com>
> (...)
>> +               data->mcp[addr]->dev = dev;
>> +               data->mcp[addr]->addr = 0x40 | (addr << 1);
> 
> What does this 0x40 mean here? Can you use a #define to specify
> exactly what is going on?

Really I am just moving the two definitions up in probe, they will get
re-written later. It is the base WRITE opcode for SPI chips.

I don't know much on this driver/HW, beyond the things I had to debug
when enabling this driver on BeagleBadge with a on board MCP23S18 chip.
So please scrutinize my changes.

Will add a constant definition and respin.

BTW I found another bug so will append to this series.

Thanks for reviewing.

~ Judith