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SubjectRe: [PATCH v4] clk: Add write operation for clk_parent debugfs node
On Thu, 7 Oct 2021 at 17:39, Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
>
> 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().
>

Cool, didn't know about that API existence. Will fix in v5.

> > + 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.
>

You're right, will be fixed in v5.

Thanks for the review!

> > +#endif
> > + }
>
> --
> With Best Regards,
> Andy Shevchenko

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