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

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Message-Id: <202310031913.27387.linux@zary.sk>
Date:   Tue, 3 Oct 2023 19:13:27 +0200
From:   Ondrej Zary <linux@...y.sk>
To:     Sergey Shtylyov <s.shtylyov@....ru>
Cc:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        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] pata_parport-fit3: implement IDE command set registers

On Monday 02 October 2023 22:06:52 Sergey Shtylyov wrote:
> On 9/30/23 10:15 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>
> > ---
> >  drivers/ata/pata_parport/fit3.c | 16 ++++------------
> >  1 file changed, 4 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/ata/pata_parport/fit3.c b/drivers/ata/pata_parport/fit3.c
> > index bad7aa920cdc..86b39966755b 100644
> > --- a/drivers/ata/pata_parport/fit3.c
> > +++ b/drivers/ata/pata_parport/fit3.c
> [...]
> > @@ -35,10 +30,11 @@
> >   * cont = 1 - access the IDE command set
> >   */
> >  
> > +static int cont_map[] = { 0x00, 0x08 };
> 
>    const?

There's no 'const' in other protocol drivers. Maybe it should be added to all of them.

> > +
> >  static void fit3_write_regr(struct pi_adapter *pi, int cont, int regr, int val)
> >  {
> > -	if (cont == 1)
> > -		return;
> > +	regr += cont_map[cont];
> 
>    Perhaps regr += cont << 3 instead?

I matched the style used by other protocol drivers.

> >  
> >  	switch (pi->mode) {
> >  	case 0:
> > @@ -59,11 +55,7 @@ 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_map[cont];
> 
>    Likewise here?
> 
> [...]
> 
> MBR, Sergey
> 


-- 
Ondrej Zary