> -----Original Message----- > From: Dmitry Torokhov [mailto:dmitry.torok...@gmail.com] > Sent: 05 June, 2015 19:41 > To: Tirdea, Irina > Cc: 'Antonio Ospite'; Bastien Nocera; linux-input@vger.kernel.org; > devicet...@vger.kernel.org; linux-ker...@vger.kernel.org > Subject: Re: [PATCH 2/9] input: goodix: fix variable length array warning > > On Fri, Jun 05, 2015 at 04:34:38PM +0000, Tirdea, Irina wrote: > > > > > > > -----Original Message----- > > > From: linux-input-ow...@vger.kernel.org > > > [mailto:linux-input-ow...@vger.kernel.org] On Behalf Of Antonio Ospite > > > Sent: 03 June, 2015 23:50 > > > To: Tirdea, Irina > > > Cc: Dmitry Torokhov; Bastien Nocera; linux-input@vger.kernel.org; > > > devicet...@vger.kernel.org; linux-ker...@vger.kernel.org > > > Subject: Re: [PATCH 2/9] input: goodix: fix variable length array warning > > > > > > On Wed, 3 Jun 2015 10:26:47 +0000 > > > "Tirdea, Irina" <irina.tir...@intel.com> wrote: > > > > > > > > -----Original Message----- > > > > > From: Antonio Ospite [mailto:a...@ao2.it] > > > > > Sent: 28 May, 2015 18:58 > > > > > To: Tirdea, Irina > > > > > Cc: Dmitry Torokhov; Bastien Nocera; linux-input@vger.kernel.org; > > > > > devicet...@vger.kernel.org; linux-ker...@vger.kernel.org > > > > > Subject: Re: [PATCH 2/9] input: goodix: fix variable length array > > > > > warning > > > > > > > > > > On Thu, 28 May 2015 15:47:38 +0300 > > > > > Irina Tirdea <irina.tir...@intel.com> wrote: > > > > > > > > > > > Fix sparse warning: > > > > > > drivers/input/touchscreen/goodix.c:182:26: warning: > > > > > > Variable length array is used. > > > > > > > > > > > > Replace the variable length array with fixed length. > > > > > > > > > > > > Signed-off-by: Irina Tirdea <irina.tir...@intel.com> > > > > > > --- > > > > > > drivers/input/touchscreen/goodix.c | 2 +- > > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > > > diff --git a/drivers/input/touchscreen/goodix.c > > > > > > b/drivers/input/touchscreen/goodix.c > > > > > > index c2e785c..dac1b3c 100644 > > > > > > --- a/drivers/input/touchscreen/goodix.c > > > > > > +++ b/drivers/input/touchscreen/goodix.c > > > > > > @@ -147,7 +147,7 @@ static void goodix_ts_report_touch(struct > > > > > > goodix_ts_data *ts, u8 *coor_data) > > > > > > */ > > > > > > static void goodix_process_events(struct goodix_ts_data *ts) > > > > > > { > > > > > > - u8 point_data[1 + GOODIX_CONTACT_SIZE * ts->max_touch_num]; > > > > > > + u8 point_data[1 + GOODIX_CONTACT_SIZE * GOODIX_MAX_CONTACTS]; > > > > > > > > > > Hi, > > > > > > > > > > > > > Hi Antonio, > > > > > > > > > this fixes the warning from sparse, but also changes the semantics of > > > > > the code: ts->max_touch_num is less that GOODIX_MAX_CONTACTS for 5 > > > > > touches devices and in this case we'll end up using more memory than > > > > > is > > > > > necessary. > > > > > > > > > > > > > I wasn't sure if it is better to save the 5 bytes or fix the warning, > > > > so I sent this to get some more input. > > > > Thanks for the feedback, I will drop this patch. > > > > > > > > > > Use kmalloc() or, alternatively, add at least a comment telling why you > > > think that sacrificing a few bytes —only for some devices— has > > > advantages over dynamic allocation. > > > > > > > You are right, kmalloc will solve both problems - the sparse warning and > > allocating > > more bytes than necessary. Don't know why I did not think of that. > > Will use that in v2. > > Please leave the patch as is. We can spare 80 bytes on the stack given > that we are running in threaded IRQ. kmallocing will use more code and > runtime resources and won't give any benefits.
I was actually thinking of allocating it with devm_kzalloc just once at device init and storing a pointer to it in the goodix_ts_data structure. Thanks, Irina > > Thanks. > > -- > Dmitry
