Messages in this thread | | | Date | Tue, 26 Feb 2008 22:03:16 +0100 | From | Marcin Slusarz <> | Subject | Re: [PATCH] video: limit stack usage of ir-kbd-i2c.c |
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On Tue, Feb 26, 2008 at 01:32:22PM +0100, Jean Delvare wrote: > Hi Marcin, > > On Mon, 25 Feb 2008 21:51:00 +0100, Marcin Slusarz wrote: > > ir_probe allocated struct i2c_client on stack; > > it's pretty big structure, so allocate it with kzalloc > > > > make checkstack output without this patch: > > x059d ir_probe [ir-kbd-i2c]: 1000 > > > > compile tested only > > > > Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com> > > Cc: Mauro Carvalho Chehab <mchehab@infradead.org> > > Cc: Jean Delvare <khali@linux-fr.org> > > --- > > drivers/media/video/ir-kbd-i2c.c | 18 +++++++++++------- > > 1 files changed, 11 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/media/video/ir-kbd-i2c.c b/drivers/media/video/ir-kbd-i2c.c > > index 9851987..aec122f 100644 > > --- a/drivers/media/video/ir-kbd-i2c.c > > +++ b/drivers/media/video/ir-kbd-i2c.c > > @@ -510,9 +510,9 @@ static int ir_probe(struct i2c_adapter *adap) > > static const int probe_cx88[] = { 0x18, 0x6b, 0x71, -1 }; > > static const int probe_cx23885[] = { 0x6b, -1 }; > > const int *probe = NULL; > > - struct i2c_client c; > > + struct i2c_client *c; > > unsigned char buf; > > - int i,rc; > > + int i, rc; > > > > switch (adap->id) { > > case I2C_HW_B_BT848: > > @@ -537,19 +537,23 @@ static int ir_probe(struct i2c_adapter *adap) > > if (NULL == probe) > > return 0; > > > > - memset(&c,0,sizeof(c)); > > - c.adapter = adap; > > + c = kzalloc(sizeof(*c), GFP_KERNEL); > > + if (!c) > > + return -ENOMEM; > > + > > + c->adapter = adap; > > for (i = 0; -1 != probe[i]; i++) { > > - c.addr = probe[i]; > > - rc = i2c_master_recv(&c,&buf,0); > > + c->addr = probe[i]; > > + rc = i2c_master_recv(c, &buf, 0); > > dprintk(1,"probe 0x%02x @ %s: %s\n", > > probe[i], adap->name, > > (0 == rc) ? "yes" : "no"); > > if (0 == rc) { > > - ir_attach(adap,probe[i],0,0); > > + ir_attach(adap, probe[i], 0, 0); > > break; > > } > > } > > + kfree(c); > > return 0; > > } > > > > While this works, I'd rather change the code to call i2c_transfer() > instead of i2c_master_recv(). i2c_transfer() is meant exactly for this > case (no i2c_client at hand.) This solves the stack usage problem > without requiring a temporary memory allocation: > > * * * * * > > Limit stack usage in ir_probe by calling i2c_transfer, which doesn't > require a struct i2c_client, instead of i2c_master_recv which does. > > Signed-off-by: Jean Delvare <khali@linux-fr.org> > --- > drivers/media/video/ir-kbd-i2c.c | 17 +++++++++-------- > 1 file changed, 9 insertions(+), 8 deletions(-) > > --- linux-2.6.25-rc3.orig/drivers/media/video/ir-kbd-i2c.c 2008-02-26 11:35:51.000000000 +0100 > +++ linux-2.6.25-rc3/drivers/media/video/ir-kbd-i2c.c 2008-02-26 11:44:54.000000000 +0100 > @@ -510,8 +510,11 @@ static int ir_probe(struct i2c_adapter * > static const int probe_cx88[] = { 0x18, 0x6b, 0x71, -1 }; > static const int probe_cx23885[] = { 0x6b, -1 }; > const int *probe = NULL; > - struct i2c_client c; > - unsigned char buf; > + struct i2c_msg msg = { > + .flags = I2C_M_RD, > + .len = 0, > + .buf = NULL, > + }; > int i,rc; > > switch (adap->id) { > @@ -537,15 +540,13 @@ static int ir_probe(struct i2c_adapter * > if (NULL == probe) > return 0; > > - memset(&c,0,sizeof(c)); > - c.adapter = adap; > for (i = 0; -1 != probe[i]; i++) { > - c.addr = probe[i]; > - rc = i2c_master_recv(&c,&buf,0); > + msg.addr = probe[i]; > + rc = i2c_transfer(adap, &msg, 1); > dprintk(1,"probe 0x%02x @ %s: %s\n", > probe[i], adap->name, > - (0 == rc) ? "yes" : "no"); > - if (0 == rc) { > + (1 == rc) ? "yes" : "no"); > + if (1 == rc) { > ir_attach(adap,probe[i],0,0); > break; > } > > > Built-tested, I've also tested loading the ir-kbd-i2c driver on an > unsupported cx88 adapter. Review and more testing welcome. I know nothing about I2C API, so I can't comment on correctness of this patch ;)
Do you have an idea (or patch :D) how to solve this: 0x00000234 v4l_compat_translate_ioctl [v4l1-compat]: 1376 ? That's on top of my make checkstack output
Marcin
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