I would like to revisit this question. Last time I complained about
this Johannes responded but he misread what mt76_mcu_send_and_get_msg()
does. I have looked at it as well and I also cannot explain what is
going on in that function.
I have looked at the callers and my first instinct is that maybe this
is dead stub code? But then when I look at mt76x02u_mcu_send_msg() I
think "No, this is not stub code. This should be returning the newly
allocated skb to the caller."
But then I think, surely at some point someone tested this code??? It
must be stub code.
Could we get some clarity on this?
regards,
dan carpenter
On Fri, Oct 08, 2021 at 05:27:35PM +0300, Dan Carpenter wrote:
> On Fri, Oct 08, 2021 at 04:03:10PM +0200, Johannes Berg wrote:
> > On Fri, 2021-10-08 at 16:00 +0300, Dan Carpenter wrote:
> > >
> > > 1146 ret = mt76_mcu_send_and_get_msg(&dev->mt76, MCU_EXT_CMD_EFUSE_ACCESS, &req,
> > > 1147 sizeof(req), true, &skb);
> > >
> > > If mt76_mcu_send_and_get_msg() calls the dev->mcu_ops->mcu_send_msg()
> > > then "skb" is not initialized.
> > >
> > > 1148 if (ret)
> > > 1149 return ret;
> > > 1150
> > > --> 1151 res = (struct mt7921_mcu_eeprom_info *)skb->data;
> >
> > Looks like possibly 'skb' is always initialized if
> > mt76_mcu_send_and_get_msg() returns 0 (success)?
> >
>
> This build is with cross function analysis enabled so Smatch looks for
> that.
>
> The problem is that the caller has to know if dev->mcu_ops->mcu_send_msg
> is NULL or not because if it's non-NULL "skb" is not set. Perhaps that
> means it should be separated into two functions and we pick which one
> to call depending on whether the pointer is set.
>
> drivers/net/wireless/mediatek/mt76/mcu.c
> 54 int mt76_mcu_send_and_get_msg(struct mt76_dev *dev, int cmd, const void *data,
> 55 int len, bool wait_resp, struct sk_buff **ret_skb)
> ^^^^^^^
> This is the parameter.
>
> 56 {
> 57 struct sk_buff *skb;
> 58
> 59 if (dev->mcu_ops->mcu_send_msg)
> 60 return dev->mcu_ops->mcu_send_msg(dev, cmd, data, len, wait_resp);
>
> The function pointer doesn't set *ret_skb at all.
>
> 61
> 62 skb = mt76_mcu_msg_alloc(dev, data, len);
> 63 if (!skb)
> 64 return -ENOMEM;
> 65
> 66 return mt76_mcu_skb_send_and_get_msg(dev, skb, cmd, wait_resp, ret_skb);
>
> But this does.
>
> 67 }
>
> regards,
> dan carpenter
