linux-kernel - Question: regmap_field_write()

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Message-ID: <e759045a-bc01-c194-35ad-42b534ccaa01@linaro.org>
Date:   Thu, 14 Jul 2022 17:01:29 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Mark Brown <broonie@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Question: regmap_field_write() - why using update?

Hi guys,

I am converting my driver using MMIO to regmap from readl/writel and to
my surprise I found that regmap_field_write() does not behave the same
as regmap_write(). I would expect that they are the same, except one
operates on fields.

However regmap_field_write() uses an update method [1] which means it
reads and performs update. regmap_write() simply writes without a read.

I find it inconsistent and a bit confusing. Any reasons for such
behavior so I won't send a patch which breaks 100 of devices?

[1]
https://elixir.bootlin.com/linux/latest/source/include/linux/regmap.h#L1307

Best regards,
Krzysztof