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 <[EMAIL PROTECTED]>
> > Cc: Mauro Carvalho Chehab <[EMAIL PROTECTED]>
> > Cc: Jean Delvare <[EMAIL PROTECTED]>
> > ---
> > 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 <[EMAIL PROTECTED]>
> ---
> 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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