netdev - RE: [PATCH] net: ti: netcp: restore get/set_pad

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Date:	Tue, 9 Feb 2016 16:37:43 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	"'Karicheri, Muralidharan'" <m-karicheri2@...com>,
	"Strashko, Grygorii" <grygorii.strashko@...com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"David S . Miller" <davem@...emloft.net>,
	"Arnd Bergmann" <arnd@...db.de>
CC:	"Cooper Jr., Franklin" <fcooper@...com>,
	"Nori, Sekhar" <nsekhar@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Kwok, WingMan" <w-kwok2@...com>,
	"N, Mugunthan V" <mugunthanvnm@...com>
Subject: RE: [PATCH] net: ti: netcp: restore get/set_pad_info() functionality

From: Karicheri, Muralidharan
> Sent: 09 February 2016 16:19
> >...
> >> >In reality the 'pad' fields ought to be renamed - since they aren't pads.
> >> >Perhaps they should be a union?
> >
> >> No. At the end of the descriptor, host software can add scratchpad
> >> which is not modified by the hardware, but is used by the driver. So
> >> please don't rename.
> >
> >So comment in the definition that the hardware doesn't modify them.
> >The driver is defining these fields and they are definitely NOT padding.
> 
> 
> It is scratch pad, not padding. Looks like pad is a confusing name. Can be
> renamed to sw_data to be in sync with spec below.
> 
> The hardware spec from
> http://www.ti.com/lit/ug/sprugr9h/sprugr9h.pdf
> 
> The other SW data portion of the descriptor exists after all of the defined
> words and is reserved for use by the host software to store completely
> private data. This region is not used in any way by the DMA or queue manager
> modules in a Multicore Navigator system and these modules will not modify
> any bytes within this region.

Right, so comment that the hardware doesn't look at the fields.
But name/type the structure fields to indicate what they contain.
Maybe sw_buf_len etc - but I suspect there are much more meaningful names.

	David