linux-kernel - Re: [PATCH v11 1/4] firmware: qcom: scm: provide a read-modify-write function

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Date: Tue, 9 Jan 2024 14:14:00 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Mukesh Ojha <quic_mojha@...cinc.com>, Mark Brown <broonie@...nel.org>
Cc: andersson@...nel.org, konrad.dybcio@...aro.org, 
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-gpio@...r.kernel.org
Subject: Re: [PATCH v11 1/4] firmware: qcom: scm: provide a read-modify-write function

On Mon, Jan 8, 2024 at 4:28 PM Mukesh Ojha <quic_mojha@...cinc.com> wrote:

> It was realized by Srinivas K. that there is a need of
> read-modify-write scm exported function so that it can
> be used by multiple clients.
>
> Let's introduce qcom_scm_io_rmw() which masks out the bits
> and write the passed value to that bit-offset.
(...)
> +int qcom_scm_io_rmw(phys_addr_t addr, unsigned int mask, unsigned int val)
> +{
> +       unsigned int old, new;
> +       int ret;
> +
> +       if (!__scm)
> +               return -EINVAL;
> +
> +       spin_lock(&__scm->lock);
> +       ret = qcom_scm_io_readl(addr, &old);
> +       if (ret)
> +               goto unlock;
> +
> +       new = (old & ~mask) | (val & mask);
> +
> +       ret = qcom_scm_io_writel(addr, new);
> +unlock:
> +       spin_unlock(&__scm->lock);
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(qcom_scm_io_rmw);

This looks a lot like you are starting to re-invent regmaps
regmap_update_bits().

If you are starting to realize you need more and more of
regmap, why not use regmap and its functions?

Yours,
Linus Walleij