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SubjectRe: [PATCH 27/31] usb/gadget/snps_udc_core: Move timer initialization earlier
Date
On Thu, Aug 31 2017, Kees Cook wrote:
> With timer initialization made earlier at the start, there is no reason
> to make del_timer_sync() calls conditionally, there by removing the
> assignments and tests of the .data field.
>
> Cc: Felipe Balbi <balbi@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Raviteja Garimella <raviteja.garimella@broadcom.com>
> Cc: Michal Nazarewicz <mina86@mina86.com>
> Cc: "Gustavo A. R. Silva" <garsilva@embeddedor.com>
> Cc: linux-usb@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> drivers/usb/gadget/udc/snps_udc_core.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/usb/gadget/udc/snps_udc_core.c b/drivers/usb/gadget/udc/snps_udc_core.c
> index 5460e5ba1c3c..1607e901e16b 100644
> --- a/drivers/usb/gadget/udc/snps_udc_core.c
> +++ b/drivers/usb/gadget/udc/snps_udc_core.c
> @@ -3067,14 +3067,12 @@ void udc_remove(struct udc *dev)
> stop_timer++;
> if (timer_pending(&udc_timer))
> wait_for_completion(&on_exit);
> - if (udc_timer.data)
> - del_timer_sync(&udc_timer);
> + del_timer_sync(&udc_timer);
> /* remove pollstall timer */
> stop_pollstall_timer++;
> if (timer_pending(&udc_pollstall_timer))
> wait_for_completion(&on_pollstall_exit);
> - if (udc_pollstall_timer.data)
> - del_timer_sync(&udc_pollstall_timer);
> + del_timer_sync(&udc_pollstall_timer);
> udc = NULL;
> }
> EXPORT_SYMBOL_GPL(udc_remove);
> @@ -3164,9 +3162,9 @@ int udc_probe(struct udc *dev)
> u32 reg;
> int retval;
>
> - /* mark timer as not initialized */
> - udc_timer.data = 0;
> - udc_pollstall_timer.data = 0;
> + /* timer init */
> + setup_timer(&udc_timer, udc_timer_function, 0);
> + setup_timer(&udc_pollstall_timer, udc_pollstall_timer_function, 0);
>
> /* device struct setup */
> dev->gadget.ops = &udc_ops;
> @@ -3206,10 +3204,6 @@ int udc_probe(struct udc *dev)
> if (retval)
> goto finished;
>
> - /* timer init */
> - setup_timer(&udc_timer, udc_timer_function, 1);
> - setup_timer(&udc_pollstall_timer, udc_pollstall_timer_function, 1);
> -
> /* set SD */
> reg = readl(&dev->regs->ctl);
> reg |= AMD_BIT(UDC_DEVCTL_SD);


Stupid question, is the check in udc_remove even necessary?

udc_probe is called from udc_plat_probe:

if (udc_probe(udc)) {
ret = -ENODEV;
goto exit_dma;
}

If the call fails, udc_plat_probe cleans up after itself and noticeably
*does not* call udc_remove. As far as I understand, if probe callback
fails, remove callback is *not* called. Meanwhile, udc_remove is called
from the remove callback which is udc_plat_remove. So, udc_remove can
be called only if udc_probe succeeds.

It seems to me that a better patch is:

--- a/drivers/usb/gadget/udc/snps_udc_core.c
+++ b/drivers/usb/gadget/udc/snps_udc_core.c
@@ -3067,14 +3067,12 @@ void udc_remove(struct udc *dev)
stop_timer++;
if (timer_pending(&udc_timer))
wait_for_completion(&on_exit);
- if (udc_timer.data)
- del_timer_sync(&udc_timer);
+ del_timer_sync(&udc_timer);
/* remove pollstall timer */
stop_pollstall_timer++;
if (timer_pending(&udc_pollstall_timer))
wait_for_completion(&on_pollstall_exit);
- if (udc_pollstall_timer.data)
- del_timer_sync(&udc_pollstall_timer);
+ del_timer_sync(&udc_pollstall_timer);
udc = NULL;
}
EXPORT_SYMBOL_GPL(udc_remove);
@@ -3164,9 +3162,9 @@ int udc_probe(struct udc *dev)
u32 reg;
int retval;

- /* mark timer as not initialized */
- udc_timer.data = 0;
- udc_pollstall_timer.data = 0;
-
/* device struct setup */
dev->gadget.ops = &udc_ops;
--
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»

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