Re: [PATCH v5 2/4] drivers/tty/serial/8250: refactor sirq and lpc address setting code

[Zev Weiss]

On Fri, Apr 09, 2021 at 12:06:16AM CDT, Andrew Jeffery wrote:
> On Thu, 8 Apr 2021, at 10:46, Zev Weiss wrote:
> > This splits dedicated aspeed_vuart_set_{sirq,lpc_address}() functions
> > out of the sysfs store functions in preparation for adding DT
> > properties that will be poking the same registers.  While we're at it,
> > these functions now provide some basic bounds-checking on their
> > arguments.
> >
> > Signed-off-by: Zev Weiss <zev@xxxxxxxxxxxxxxxxx>
> > ---
> >  drivers/tty/serial/8250/8250_aspeed_vuart.c | 51 ++++++++++++++-------
> >  1 file changed, 35 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > b/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > index c33e02cbde93..8433f8dbb186 100644
> > --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > @@ -72,22 +72,31 @@ static ssize_t lpc_address_show(struct device *dev,
> >  	return snprintf(buf, PAGE_SIZE - 1, "0x%x\n", addr);
> >  }
> >
> > +static int aspeed_vuart_set_lpc_address(struct aspeed_vuart *vuart, u32 addr)
> > +{
> > +	if (addr > U16_MAX)
> > +		return -EINVAL;
> > +
> > +	writeb(addr >> 8, vuart->regs + ASPEED_VUART_ADDRH);
> > +	writeb(addr >> 0, vuart->regs + ASPEED_VUART_ADDRL);
> > +
> > +	return 0;
> > +}
> > +
> >  static ssize_t lpc_address_store(struct device *dev,
> >  				 struct device_attribute *attr,
> >  				 const char *buf, size_t count)
> >  {
> >  	struct aspeed_vuart *vuart = dev_get_drvdata(dev);
> > -	unsigned long val;
> > +	u32 val;
> >  	int err;
> >
> > -	err = kstrtoul(buf, 0, &val);
> > +	err = kstrtou32(buf, 0, &val);
> >  	if (err)
> >  		return err;
> >
> > -	writeb(val >> 8, vuart->regs + ASPEED_VUART_ADDRH);
> > -	writeb(val >> 0, vuart->regs + ASPEED_VUART_ADDRL);
> > -
> > -	return count;
> > +	err = aspeed_vuart_set_lpc_address(vuart, val);
> > +	return err ? : count;
> >  }
> >
> >  static DEVICE_ATTR_RW(lpc_address);
> > @@ -105,27 +114,37 @@ static ssize_t sirq_show(struct device *dev,
> >  	return snprintf(buf, PAGE_SIZE - 1, "%u\n", reg);
> >  }
> >
> > +static int aspeed_vuart_set_sirq(struct aspeed_vuart *vuart, u32 sirq)
> > +{
> > +	u8 reg;
> > +
> > +	if (sirq > (ASPEED_VUART_GCRB_HOST_SIRQ_MASK >> ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT))
> > +		return -EINVAL;
> > +
> > +	sirq <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
> > +	sirq &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
>
> This might be less verbose if we reordered things a little:
>
> ```
> sirq <<= ASPEED_VUART_GCRB_HOST_SIRQ_SHIFT;
> if (sirq & ASPEED_VUART_GCRB_HOST_SIRQ_MASK)
> 	return -EINVAL;
> sirq &= ASPEED_VUART_GCRB_HOST_SIRQ_MASK;
> ```

Hmm, that (or something similar, perhaps with a '~' on the mask in the 
if condition?) does seem like it'd be a nice improvement, though I 
suppose it'd also mean we'd fail to reject some way-out-of-range sirq 
values (e.g. if it had its MSB set) -- so I think I'll leave it as is, 
just in the name of thoroughness/paranoia?

> But otherwise it looks okay, so
>
> Reviewed-by: Andrew Jeffery <andrew@xxxxxxxx>

Thanks.