linux-kernel - Re: [PATCH] clk: microchip: mpfs-ccc: Use devm_kasprintf() for allocating formatted strings

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Message-ID: <Y7WBtMmLzYvk60tD@spud>
Date:   Wed, 4 Jan 2023 13:40:04 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: microchip: mpfs-ccc: Use devm_kasprintf() for
 allocating formatted strings

On Wed, Jan 04, 2023 at 02:26:53PM +0100, Geert Uytterhoeven wrote:
> Hi Conor,
> 
> On Tue, Jan 3, 2023 at 6:32 PM Conor Dooley <conor@...nel.org> wrote:

> > I half wonder if this should actually have a fixes tag too. Since it
> > used what came after the @ in $full_name, it'd be possible to create
> > (an incorrect) DTS that would lead to a clash between pll names &
> > therefore probe would fail.
> > The tag would be:
> > Fixes: d39fb172760e ("clk: microchip: add PolarFire SoC fabric clock support")
> 
> But I don't change any of that in my patch?
> /me confused.

The numbers in there were chosen to fit exactly what is in mpfs.dtsi
(IOW the correct node address), so doing
@@ -201,14 +200,13 @@ static int mpfs_ccc_register_plls(struct device *dev, struct mpfs_ccc_pll_hw_clo
 
 	for (unsigned int i = 0; i < num_clks; i++) {
 		struct mpfs_ccc_pll_hw_clock *pll_hw = &pll_hws[i];
-		char *name = devm_kzalloc(dev, 18, GFP_KERNEL);
 
-		if (!name)
+		pll_hw->name = devm_kasprintf(dev, GFP_KERNEL, "ccc%s_pll%u",
+					      strchrnul(dev->of_node->full_name, '@'), i);
+		if (!pll_hw->name)
 			return -ENOMEM;
 
 		pll_hw->base = data->pll_base[i];
-		snprintf(name, 18, "ccc%s_pll%u", strchrnul(dev->of_node->full_name, '@'), i);
-		pll_hw->name = (const char *)name;
 		pll_hw->hw.init = CLK_HW_INIT_PARENTS_DATA_FIXED_SIZE(pll_hw->name,
 								      pll_hw->parents,
 								      &mpfs_ccc_pll_ops, 0);

means that we no longer have to worry that someone would provide a
device tree with a node address that would make "ccc<node_address>_pll<N>"
exceed 18 characters. If that happened, the <N> would be cut off & both
pll 0 & 1 would be named identically. If that happens, pll1 would fail
to register.

Or am I misunderstanding something? Probably am..

Thanks,
Conor.


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