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

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Message-ID: <YG/7sFv+2AlLKbZ5@hatter.bewilderbeest.net>
Date:   Fri, 9 Apr 2021 02:01:04 -0500
From:   Zev Weiss <zev@...ilderbeest.net>
To:     Andrew Jeffery <andrew@...id.au>
Cc:     Joel Stanley <joel@....id.au>, openbmc@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org
Subject: Re: [PATCH v5 2/4] drivers/tty/serial/8250: refactor sirq and lpc
 address setting code

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@...ilderbeest.net>
>> ---
>>  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@...id.au>
>

Thanks.