netdev - Re: [PATCH net 2/4] rtl8150: Use heap buffers for all register access

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Message-ID: <20170207145244.ff5uffxb66wyezqz@p310>
Date:   Tue, 7 Feb 2017 16:52:44 +0200
From:   Petko Manolov <petkan@...leusys.com>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     Greg KH <greg@...ah.com>, Ben Hutchings <ben@...adent.org.uk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH net 2/4] rtl8150: Use heap buffers for all register access

On 17-02-07 14:14:30, David Laight wrote:
> From: Petko Manolov
> > Sent: 07 February 2017 13:21
> ...
> > > > Would you consider what David proposed (usb_control_msg_with_malloc()) for 4.11,
> > > > for example?  I for one will use something like that in all my drivers.
> > >
> > > Sure, but you might want to make it a bit smaller of a function name :)
> > 
> > Whatever i say may be taken as volunteering. :D
> > 
> > Second - i've got really bad taste when naming things.  asdfgl() is a short name
> > although not very descriptive. ;)
> ...
> 
> Actually, for short control transfers a field in the urb itself could be used 
> (unless another 8 bytes makes the structure larger).
> 
> IIRC for xhci, the 8 byte pointer field can be marked as containing the actual 
> data - saving the hardware from doing another dma as well.

Unless set up for automatic triggering, 8 byte DMA transfer is an overkill (by 
means of having to program a bunch of IO registers), especially on a 64bit 
machine.

However, not knowing the USB host controllers specifics i'll shut up.


cheers,
Petko