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SubjectRe: [PATCH v4] clk: Add write operation for clk_parent debugfs node
On Thu, Oct 7, 2021 at 5:09 PM Sam Protsenko <semen.protsenko@linaro.org> wrote:
>
> Useful for testing mux clocks. One can write the index of the parent to
> be set into clk_parent node, starting from 0. Example
>
> # cd /sys/kernel/debug/clk/mout_peri_bus
> # cat clk_possible_parrents
> dout_shared0_div4 dout_shared1_div4
> # cat clk_parent
> dout_shared0_div4
> # echo 1 > clk_parent
> # cat clk_parent
> dout_shared1_div4
>
> CLOCK_ALLOW_WRITE_DEBUGFS has to be defined in drivers/clk/clk.c in
> order to use this feature.

...

> +static ssize_t current_parent_write(struct file *file, const char __user *ubuf,
> + size_t count, loff_t *ppos)
> +{
> + struct seq_file *s = file->private_data;
> + struct clk_core *core = s->private;
> + struct clk_core *parent;

> + char buf[4] = { 0 };

We may use {} (in a more standardized way), but see below.

> + u8 idx;
> + int err;

> + if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
> + return -EFAULT;
> +
> + err = kstrtou8(buf, 0, &idx);
> + if (err)
> + return err;

NIH kstrotu8_from_user().

> + parent = clk_core_get_parent_by_index(core, idx);
> + if (!parent)
> + return -ENOENT;
> +
> + clk_prepare_lock();
> + err = clk_core_set_parent_nolock(core, parent);
> + clk_prepare_unlock();
> + if (err)
> + return err;
> +
> + return count;
> +}

...

> +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
> + if (core->num_parents > 1) {
> + debugfs_create_file("clk_parent", 0644, root, core,
> + &current_parent_rw_fops);

> + } else {
> + debugfs_create_file("clk_parent", 0444, root, core,
> + &current_parent_fops);
> + }
> +#else
> debugfs_create_file("clk_parent", 0444, root, core,
> &current_parent_fops);

Dup. You can avoid it.

> +#endif
> + }

--
With Best Regards,
Andy Shevchenko

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