[PATCH] can: flexcan: Fix an uninitialized variable issue

[PATCH] can: flexcan: Fix an uninitialized variable issue

[Christophe JAILLET]

If both 'clk_ipg' and 'clk_per' are NULL, we return an un-init value.
So set 'err' to 0, to return success in such a case.

Fixes: d9cead75b1c6 ("can: flexcan: add mcf5441x support")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Another way to fix it is to remove the NULL checks for 'clk_ipg' and
'clk_per' that been added in commit d9cead75b1c6.

They look useless to me because 'clk_prepare_enable()' returns 0 if it is
passed a NULL pointer.
Having these explicit tests is maybe informational (i.e. these pointers
can really be NULL) or have been added to silent a compiler or a static
checker.

So, in case, I've left the tests and just fixed the un-init 'err' variable
issue.
---
 drivers/net/can/flexcan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 54ffb796a320..7734229aa078 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -649,7 +649,7 @@ static inline void flexcan_error_irq_disable(const struct flexcan_priv *priv)
 
 static int flexcan_clks_enable(const struct flexcan_priv *priv)
 {
-	int err;
+	int err = 0;
 
 	if (priv->clk_ipg) {
 		err = clk_prepare_enable(priv->clk_ipg);
-- 
2.30.2

Re: [PATCH] can: flexcan: Fix an uninitialized variable issue

[Marc Kleine-Budde]

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On 29.07.2021 13:27:42, Christophe JAILLET wrote:
> If both 'clk_ipg' and 'clk_per' are NULL, we return an un-init value.
> So set 'err' to 0, to return success in such a case.

Thanks for the patch, a similar one has been posted before:
https://lore.kernel.org/linux-can/20210728075428.1493568-1-mkl@pengutronix.de/

> Fixes: d9cead75b1c6 ("can: flexcan: add mcf5441x support")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> Another way to fix it is to remove the NULL checks for 'clk_ipg' and
> 'clk_per' that been added in commit d9cead75b1c6.
> 
> They look useless to me because 'clk_prepare_enable()' returns 0 if it is
> passed a NULL pointer.

ACK, while the common clock framework's clk_prepare_enable() can handle
NULL pointers, the clock framework used on the mcf5441x doesn't.

> Having these explicit tests is maybe informational (i.e. these pointers
> can really be NULL) or have been added to silent a compiler or a static
> checker.
> 
> So, in case, I've left the tests and just fixed the un-init 'err' variable
> issue.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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Re: [PATCH] can: flexcan: Fix an uninitialized variable issue

[Dan Carpenter]

On Thu, Jul 29, 2021 at 01:31:01PM +0200, Marc Kleine-Budde wrote:
> On 29.07.2021 13:27:42, Christophe JAILLET wrote:
> > If both 'clk_ipg' and 'clk_per' are NULL, we return an un-init value.
> > So set 'err' to 0, to return success in such a case.
> 
> Thanks for the patch, a similar one has been posted before:
> https://lore.kernel.org/linux-can/20210728075428.1493568-1-mkl@pengutronix.de/
> 
> > Fixes: d9cead75b1c6 ("can: flexcan: add mcf5441x support")
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> > ---
> > Another way to fix it is to remove the NULL checks for 'clk_ipg' and
> > 'clk_per' that been added in commit d9cead75b1c6.
> > 
> > They look useless to me because 'clk_prepare_enable()' returns 0 if it is
> > passed a NULL pointer.
> 
> ACK, while the common clock framework's clk_prepare_enable() can handle
> NULL pointers, the clock framework used on the mcf5441x doesn't.

Huh?  It looks like it just uses the regular stuff?

regards,
dan carpenter

Re: [PATCH] can: flexcan: Fix an uninitialized variable issue

[Marc Kleine-Budde]

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On 29.07.2021 14:44:42, Dan Carpenter wrote:
> On Thu, Jul 29, 2021 at 01:31:01PM +0200, Marc Kleine-Budde wrote:
> > On 29.07.2021 13:27:42, Christophe JAILLET wrote:
> > > If both 'clk_ipg' and 'clk_per' are NULL, we return an un-init value.
> > > So set 'err' to 0, to return success in such a case.
> > 
> > Thanks for the patch, a similar one has been posted before:
> > https://lore.kernel.org/linux-can/20210728075428.1493568-1-mkl@pengutronix.de/
> > 
> > > Fixes: d9cead75b1c6 ("can: flexcan: add mcf5441x support")
> > > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> > > ---
> > > Another way to fix it is to remove the NULL checks for 'clk_ipg' and
> > > 'clk_per' that been added in commit d9cead75b1c6.
> > > 
> > > They look useless to me because 'clk_prepare_enable()' returns 0 if it is
> > > passed a NULL pointer.
> > 
> > ACK, while the common clock framework's clk_prepare_enable() can handle
> > NULL pointers, the clock framework used on the mcf5441x doesn't.
> 
> Huh?  It looks like it just uses the regular stuff?

https://lore.kernel.org/linux-can/CAMuHMdUeeH2BWgVRoVX7yfckY=wi8X3qkaH0THhVF_3FpZsbqg@mail.gmail.com/
Geert Uytterhoeven said:

>> Except that the non-CCF implementation of clk_enable() in
>> arch/m68k/coldfire/clk.c still returns -EINVAL instead of NULL.
>> Any plans to move to CCF? Or at least fix legacy clk_enable().

https://lore.kernel.org/linux-can/7c1151fc-cc28-cbc0-c385-313428b32dd7@kernel-space.org/
Angelo Dureghello said:
>> as Geert pointed out, right now without this protection
>> (that shouldn't anyway harm), probe fails:
>> 
>> [    1.680000] flexcan: probe of flexcan.0 failed with error -22

Maybe it's time to fix the mcf5441x's clk_enable() as Geert pointed out.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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Re: [PATCH] can: flexcan: Fix an uninitialized variable issue

[Dan Carpenter]

On Thu, Jul 29, 2021 at 01:57:44PM +0200, Marc Kleine-Budde wrote:
> Maybe it's time to fix the mcf5441x's clk_enable() as Geert pointed out.

Ah.  Thanks!  I'll send a patch for that.  In the mean time your patch
which sets "ret = 0;" is the correct fix.

regards,
dan carpenter