linux-kernel - Using regmap_update_bits to update a write only register

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Message-ID: <CAEnQRZAKiw8iJdy8_McqU1zewWMOTr_x0eopcKLOrKokjDgsXA@mail.gmail.com>
Date:	Thu, 5 Mar 2015 19:35:32 +0200
From:	Daniel Baluta <daniel.baluta@...il.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	broonie@...nel.org
Subject: Using regmap_update_bits to update a write only register

Hi Mark,

Is it possible to use regmap_update_bits to update the values
of some bits in a write only register?

I was hoping that by filling the .reg_defaults field of regmap_config
the regmap_update_bits function will not try to read the register
from hardware.

Instead I think first call of regmap_update_bits will try to read the register
from hardware, but this fails with -EIO because the register is marked as
write only.

Am I doing something wrong?

thanks,
Daniel.
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