linux-kernel - Re: [PATCH v2 3/3] net: netcp: rework the code for get/set sw

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Date:	Fri, 19 Feb 2016 17:21:57 -0500
From:	Murali Karicheri <m-karicheri2@...com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
	<davem@...emloft.net>
Subject: Re: [PATCH v2 3/3] net: netcp: rework the code for get/set sw_data in
 dma desc

On 02/19/2016 03:55 PM, Arnd Bergmann wrote:
> On Friday 19 February 2016 12:58:44 Murali Karicheri wrote:
>> SW data field in descriptor can be used by software to hold private
>> data for the driver. As there are 4 words available for this purpose,
>> use separate macros to place it or retrieve the same to/from
>> descriptors. Also do type cast of data types accordingly.
>>
>> Cc: Wingman Kwok <w-kwok2@...com>
>> Cc: Mugunthan V N <mugunthanvnm@...com>
>> CC: Arnd Bergmann <arnd@...db.de>
>> CC: Grygorii Strashko <grygorii.strashko@...com>
>> CC: David Laight <David.Laight@...LAB.COM>
>> Signed-off-by: Murali Karicheri <m-karicheri2@...com>
> 
> Looks ok in principle.
> 
> Acked-by: Arnd Bergmann <arnd@...db.de>
> 
>>  		get_pkt_info(&dma_buf, &tmp, &dma_desc, ndesc);
>> -		get_sw_data((u32 *)&buf_ptr, &buf_len, ndesc);
>> +		/* warning!!!! We are retrieving the virtual ptr in the sw_data
>> +		 * field as a 32bit value. Will not work on 64bit machines
>> +		 */
>> +		buf_ptr = (void *)GET_SW_DATA0(ndesc);
>> +		buf_len = (int)GET_SW_DATA1(desc);
> 
> I would have abstracted the retrieval of a pointer again,
> and added the comment in the helper function once, it doesn't
> really need to be duplicated everywhere.
> 
Arnd,

I thought about it to add it to the API. API currently set buffer
and ptr. It would be an issue only if store/retrieve ptr in/from the sw_data.
So for the comment to be really useful to someone who is changing the code,
doesn't it make sense to add it at the point of invocation as done in this
patch? No?

Murali

> 	Arnd
> 


-- 
Murali Karicheri
Linux Kernel, Keystone