linux-kernel - Re: [PATCH 4/4] ata: pata_parport: fit3: implement IDE command set registers

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Message-Id: <202310052246.37625.linux@zary.sk>
Date:   Thu, 5 Oct 2023 22:46:37 +0200
From:   Ondrej Zary <linux@...y.sk>
To:     Sergey Shtylyov <s.shtylyov@....ru>
Cc:     Damien Le Moal <dlemoal@...nel.org>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Christoph Hellwig <hch@....de>, Tim Waugh <tim@...erelk.net>,
        linux-parport@...ts.infradead.org, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] ata: pata_parport: fit3: implement IDE command set registers

On Thursday 05 October 2023 21:53:44 Sergey Shtylyov wrote:
> On 10/5/23 10:24 PM, Ondrej Zary wrote:
> 
> > fit3 protocol driver does not support accessing IDE control registers
> > (device control/altstatus). The DOS driver does not use these registers
> > either (as observed from DOSEMU trace). But the HW seems to be capable
> > of accessing these registers - I simply tried bit 3 and it works!
> > 
> > The control register is required to properly reset ATAPI devices or
> > they will be detected only once (after a power cycle).
> > 
> > Tested with EXP Computer CD-865 with MC-1285B EPP cable and
> > TransDisk 3000.
> > 
> > Signed-off-by: Ondrej Zary <linux@...y.sk>
> 
> Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>
> 
> > ---
> >  drivers/ata/pata_parport/fit3.c | 14 ++------------
> >  1 file changed, 2 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/ata/pata_parport/fit3.c b/drivers/ata/pata_parport/fit3.c
> > index bad7aa920cdc..d2b81cf2e16d 100644
> > --- a/drivers/ata/pata_parport/fit3.c
> > +++ b/drivers/ata/pata_parport/fit3.c
> [...]
> > @@ -59,11 +53,7 @@ static int fit3_read_regr(struct pi_adapter *pi, int cont, int regr)
> >  {
> >  	int  a, b;
> >  
> > -	if (cont) {
> > -		if (regr != 6)
> > -			return 0xff;
> > -		regr = 7;
> > -	}
> > +	regr += cont << 3;
> 
>    So, is regr == 7 instead of 8 intentional?

The original code read ATA_REG_STATUS (7) in context 0 instead of ALT_STATUS (6) in context 1.

-- 
Ondrej Zary