Date:   Tue, 12 Feb 2019 16:26:00 +0100
From:   Stanislaw Gruszka <sgruszka@redhat.com>
To:     Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Cc:     Felix Fietkau <nbd@nbd.name>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        lorenzo@kernel.org
Subject: Re: [PATCH 0/4] do not use sg if not properly supported by usb
 controller
Message-ID: <20190212152559.GB23126@redhat.com>
References: <cover.1549977282.git.lorenzo@kernel.org>
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 <20190212141725.GD12906@redhat.com>
 <20190212142528.GB24197@localhost.localdomain>
 <20190212145424.GE12906@redhat.com>
 <20190212150836.GA10823@localhost.localdomain>
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On Tue, Feb 12, 2019 at 04:08:37PM +0100, Lorenzo Bianconi wrote:
> > > > What unnecessary operation ?
> > > 
> > > the ones in mt76u_fill_bulk_urb()
> > 
> > Your patches also add extra operations on hotpath due to urb->num_sgs and
> > dev->usb.sg_en checks.
> 
> here I guess you should use mt76u_check_sg() instead of
> udev->bus->sg_tablesize > 0 so I think you need to precompute it since it is in
> the hotpath

It's not necessary. If udev->bus->sg_tablesize > 0 is true and rest
of mt76u_check_sg() is not, we will submit urb with urb->num_sgs = 1 to
usb host driver, what is fine. 

> Moreover the RFC series has been tested by multiple users and on multiple
> devices

I know. Perhaps you could test my patch on rpi ?

Stanislaw