netdev - Re: [PATCH, resubmit] ax88179_178a: ASIX AX88179_178A USB 3.0/2.0 to gigabit ethernet adapter driver

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Date:	Fri, 08 Feb 2013 11:41:47 +0800
From:	Freddy <freddy@...x.com.tw>
To:	Ben Hutchings <bhutchings@...arflare.com>
CC:	netdev@...r.kernel.org, davem@...emloft.net,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH, resubmit] ax88179_178a: ASIX AX88179_178A USB 3.0/2.0
 to gigabit ethernet adapter driver

On 02/08/2013 04:02 AM, Ben Hutchings wrote:
> On Thu, 2013-02-07 at 21:39 +0800, Freddy Xin wrote:
>> From: Freddy Xin <freddy@...x.com.tw>
>>
>> This is a resubmission.
>> Added "const" to ethtool_ops structure and fixed the coding style of AX88179_BULKIN_SIZE array.
>> Fixed the issue that the default MTU is not 1500.
>> Added ax88179_change_mtu function and enabled the hardware jumbo frame function to support an
>> MTU higher than 1500.
>> Fixed indentation and empty line coding style errors.
>> The _nopm version usb functions were added to access register in suspend and resume functions.
>> Serveral variables allocted dynamically were removed and replaced by stack variables.
>> ax88179_get_eeprom were modified from asix_get_eeprom in asix_common.
>>
>> This patch adds a driver for ASIX's AX88179 family of USB 3.0/2.0
>> to gigabit ethernet adapters. It's based on the AX88xxx driver but
>> the usb commands used to access registers for AX88179 are completely different.
>> This driver had been verified on x86 system with AX88179/AX88178A and
>> Sitcomm LN-032 USB dongles.
>>
>> Signed-off-by: Freddy Xin <freddy@...x.com.tw>
> [...]
>> --- /dev/null
>> +++ b/drivers/net/usb/ax88179_178a.c
> [...]
>> +struct ax88179_data {
>> +       u16 rxctl;
>> +};
> Should also be declared __packed, as on some architectures it may be
> padded to 4 bytes.
>
> rxctl is presumably required to be little-endian (__le16)?
>
>> +struct ax88179_int_data {
>> +       u16 res1;
>> +       u8 link;
>> +       u16 res2;
>> +       u8 status;
>> +       u16 res3;
>> +} __packed;
> Same here, the u16 fields are presumably little-endian?
>
> [...]
>> +struct ax88179_rx_pkt_header {
>> +	u8	l4_csum_err:1,
>> +		l3_csum_err:1,
>> +		l4_type:3,
>> +		l3_type:2,
>> +		ce:1;
>> +
>> +	u8	vlan_ind:3,
>> +		rx_ok:1,
>> +		pri:3,
>> +		bmc:1;
>> +
>> +	u16	len:13,
>> +		crc:1,
>> +		mii:1,
>> +		drop:1;
>> +} __packed;
> This won't work on both big-endian systems (assuming this works on x86).
> You apparently try to convert the structure in-place in
> ax88179_rx_fixup() by calling le32_to_cpus(); that may work if you
> define all the bitfields to be part of a u32 but it won't work with the
> current definition.
>
> [...]
>> +static int
>> +ax88179_set_features(struct net_device *net, netdev_features_t features)
>> +{
>> +	u8 tmp;
>> +	struct usbnet *dev = netdev_priv(net);
>> +	netdev_features_t changed = net->features ^ features;
>> +
>> +	if (changed & NETIF_F_TSO)
>> +		net->features ^= NETIF_F_TSO;
>> +
>> +	if (changed & NETIF_F_SG)
>> +		net->features ^= NETIF_F_SG;
> Don't change net->features; the caller will do that for you.
>
>> +       if (changed & NETIF_F_IP_CSUM) {
>> +               ax88179_read_cmd(dev, AX_ACCESS_MAC, AX_TXCOE_CTL, 1, 1, &tmp);
>> +               tmp ^= AX_TXCOE_TCP | AX_TXCOE_UDP;
>> +               ax88179_write_cmd(dev, AX_ACCESS_MAC, AX_TXCOE_CTL, 1, 1, &tmp);
>> +
>> +               net->features ^= NETIF_F_IP_CSUM;
>> +       }
> [...]
>
> Isn't tmp going to be in little-endian byte order, so this doesn't work
> correctly on a big-endian system?
>
> There are a lot of reads and writes of 16-bit registers using
> ax88179_{read,write}_cmd(); maybe you should add
> ax88179_{read,write}_le16() to handle this specific case.
>
> Ben.
>
Thank you, Ben. I will fix bugs and test it on a big-endian system.

Freddy
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