linux-kernel - Re: [PATCH 3/3] dm9601: add support ethtool style utility

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Date:	Thu, 10 Mar 2016 11:49:20 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Joseph CHANG <josright123@...il.com>,
	Peter Korsgaard <jacmet@...site.dk>, netdev@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Joseph Chang <joseph_chang@...icom.com.tw>
Subject: Re: [PATCH 3/3] dm9601: add support ethtool style utility

The subject line on this is very vague; it should say which ethtool
operation you're implementing.

On Thu, 2016-03-10 at 19:24 +0800, Joseph CHANG wrote:

> Add function dm9601_set_eeprom which tested good with ethtool
> utility, include the eeprom words dump and the eeprom byte write.
> 
> Signed-off-by: Joseph CHANG <josright123@...il.com>
> ---
>  drivers/net/usb/dm9601.c | 39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/net/usb/dm9601.c b/drivers/net/usb/dm9601.c
> index 50095df..a6904f4 100644
> --- a/drivers/net/usb/dm9601.c
> +++ b/drivers/net/usb/dm9601.c
> @@ -61,6 +61,7 @@
>  #define DM_RX_OVERHEAD	7	/* 3 byte header + 4 byte crc tail */
>  #define DM_TIMEOUT	1000
>  #define	DM_EP3I_VAL	0x07
> +#define	MD96XX_EEPROM_MAGIC	0x9620

The get_eeprom operation needs to be changed, to set eeprom->magic to
this value.

>  static int dm_read(struct usbnet *dev, u8 reg, u16 length, void *data)
>  {
> @@ -289,6 +290,43 @@ static int dm9601_get_eeprom(struct net_device *net,
>  	return 0;
>  }
>  
> +static int dm9601_set_eeprom(struct net_device *net,
> +			     struct ethtool_eeprom *eeprom, u8 *data)
> +{
> +	struct usbnet *dev = netdev_priv(net);
> +	int offset = eeprom->offset;
> +	int len = eeprom->len;
> +	int done;
> +
> +	if (eeprom->magic != MD96XX_EEPROM_MAGIC) {
> +		netdev_dbg(dev->net, "EEPROM: magic value mismatch, magic = 0x%x",
> +			   eeprom->magic);
> +		return -EINVAL;
> +	}
> +
> +	while (len > 0) {
> +		if (len & 1 || offset & 1) {

Given that the get_eeprom operation only handles word-aligned reads, is
it really important to support misaligned writes in set_eeprom?

Also, this test should be 'if (len == 1 || offset & 1)'.  Consider a
write with offset = 2, len = 3.  You want to write a word on the first
iteration, then a byte on the second iteration.

> +			int which = offset & 1;
> +			u8 tmp[2];
> +
> +			dm_read_eeprom_word(dev, offset / 2, tmp);
> +			tmp[which] = *data;
> +			dm_write_eeprom_word(dev, offset / 2,
> +					     tmp[0] | tmp[1] << 8);
> +			mdelay(10);

Why is a delay required here, but not in the other case?

> +			done = 1;
> +		} else {
> +			dm_write_eeprom_word(dev, offset / 2,
> +					     data[0] | data[1] << 8);
> +			done = 2;
> +		}
> +		data += done;
> +		offset += done;
> +		len -= done;
> +	}
> +	return 0;
> +}
[...]

Ben.

-- 
Ben Hutchings
To err is human; to really foul things up requires a computer.
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