Re: [PATCH 2/9] usb: cdns3: Improvement: removed not needed variables initialization

Dan Carpenter
2020-07-07T10:17:50Z

On Tue, Jul 07, 2020 at 06:23:32AM +0000, Peter Chen wrote:
> On 20-07-01 08:19:57, Pawel Laszczak wrote:
> > Patch remove some variables initialization from core.c and drd.c
> > file.
> >
> > Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> > ---
> > drivers/usb/cdns3/core.c | 4 ++--
> > drivers/usb/cdns3/drd.c | 19 +++++++++----------
> > 2 files changed, 11 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
> > index eaafa6bd2a50..c3dac945f63d 100644
> > --- a/drivers/usb/cdns3/core.c
> > +++ b/drivers/usb/cdns3/core.c
> > @@ -86,7 +86,7 @@ static int cdns3_core_init_role(struct cdns3 *cdns)
> > struct device *dev = cdns->dev;
> > enum usb_dr_mode best_dr_mode;
> > enum usb_dr_mode dr_mode;
> > - int ret = 0;
> > + int ret;
> >
> > dr_mode = usb_get_dr_mode(dev);
> > cdns->role = USB_ROLE_NONE;
> > @@ -177,7 +177,7 @@ static int cdns3_core_init_role(struct cdns3 *cdns)
> > goto err;
> > }
> >
> > - return ret;
> > + return 0;
> > err:
> > cdns3_exit_roles(cdns);
> > return ret;
> > diff --git a/drivers/usb/cdns3/drd.c b/drivers/usb/cdns3/drd.c
> > index 58089841ed52..4939a568d8a2 100644
> > --- a/drivers/usb/cdns3/drd.c
> > +++ b/drivers/usb/cdns3/drd.c
> > @@ -29,7 +29,6 @@
> > */
> > int cdns3_set_mode(struct cdns3 *cdns, enum usb_dr_mode mode)
> > {
> > - int ret = 0;
> > u32 reg;
> >
> > switch (mode) {
> > @@ -61,7 +60,7 @@ int cdns3_set_mode(struct cdns3 *cdns, enum usb_dr_mode mode)
> > return -EINVAL;
> > }
> >
> > - return ret;
> > + return 0;
> > }
> >
> > int cdns3_get_id(struct cdns3 *cdns)
> > @@ -134,11 +133,11 @@ static void cdns3_otg_enable_irq(struct cdns3 *cdns)
> > int cdns3_drd_switch_host(struct cdns3 *cdns, int on)
> > {
> > int ret, val;
> > - u32 reg = OTGCMD_OTG_DIS;
> >
> > /* switch OTG core */
> > if (on) {
> > - writel(OTGCMD_HOST_BUS_REQ | reg, &cdns->otg_regs->cmd);
> > + writel(OTGCMD_HOST_BUS_REQ | OTGCMD_OTG_DIS,
> > + &cdns->otg_regs->cmd);
> >
> > dev_dbg(cdns->dev, "Waiting till Host mode is turned on\n");
> > ret = readl_poll_timeout_atomic(&cdns->otg_regs->sts, val,
> > @@ -212,7 +211,7 @@ int cdns3_drd_switch_gadget(struct cdns3 *cdns, int on)
> > */
> > static int cdns3_init_otg_mode(struct cdns3 *cdns)
> > {
> > - int ret = 0;
> > + int ret;
> >
> > cdns3_otg_disable_irq(cdns);
> > /* clear all interrupts */
> > @@ -223,7 +222,8 @@ static int cdns3_init_otg_mode(struct cdns3 *cdns)
> > return ret;
> >
> > cdns3_otg_enable_irq(cdns);
> > - return ret;
> > +
> > + return 0;
> > }
> >
> > /**
> > @@ -234,7 +234,7 @@ static int cdns3_init_otg_mode(struct cdns3 *cdns)
> > */
> > int cdns3_drd_update_mode(struct cdns3 *cdns)
> > {
> > - int ret = 0;
> > + int ret;
> >
> > switch (cdns->dr_mode) {
> > case USB_DR_MODE_PERIPHERAL:
> > @@ -307,8 +307,8 @@ static irqreturn_t cdns3_drd_irq(int irq, void *data)
> > int cdns3_drd_init(struct cdns3 *cdns)
> > {
> > void __iomem *regs;
> > - int ret = 0;
> > u32 state;
> > + int ret;
> >
> > regs = devm_ioremap_resource(cdns->dev, &cdns->otg_res);
> > if (IS_ERR(regs))
> > @@ -359,7 +359,6 @@ int cdns3_drd_init(struct cdns3 *cdns)
> > cdns3_drd_thread_irq,
> > IRQF_SHARED,
> > dev_name(cdns->dev), cdns);
> > -
> > if (ret) {
> > dev_err(cdns->dev, "couldn't get otg_irq\n");
> > return ret;
> > @@ -371,7 +370,7 @@ int cdns3_drd_init(struct cdns3 *cdns)
> > return -ENODEV;
> > }
> >
> > - return ret;
> > + return 0;
>
> Is this necessary?
>

"return ret;" is not immediately clear like a "return 0;". I review a
lot of return values so it's really important that the code is clear.
I'm looking for places which return both postives and negatives. These
should always be documented but the majority are not.

Also another thing is that when people do:

ret = some_function();
if (!ret)
return ret;

I review all of those because a bug that we sometimes see is that the
if statement is reversed and the ! should be removed. A third thing is
that people sometimes do silly things with the last if statement in the
function.

ret = one();
if (ret)
return ret;

ret = two();
if (ret)
goto free_one;

ret = three();
if (!ret)
return ret; // <-- UGH!!!!

free(two);
free_one:
free(one);

Please look for this and tell people to not write code like that. It's
always better to do failure handling instead of success handling.

regards,
dan carpenter