linux-kernel - Re: [PATCH 3/3] NCR5380: Check for chip presence in NCR5380

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Date:   Mon, 31 Oct 2016 14:29:50 +1100 (AEDT)
From:   Finn Thain <fthain@...egraphics.com.au>
To:     Ondrej Zary <linux@...nbow-software.org>
cc:     Christoph Hellwig <hch@...radead.org>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] NCR5380: Check for chip presence in NCR5380_init()


On Sun, 30 Oct 2016, Ondrej Zary wrote:

> Read back MODE_REG after writing it in NCR5380_init() to check if the
> chip is really there.
> 
> This prevents hang when incorrect I/O address was specified by user.

Do you know whereabouts in the driver the hang happens? Maybe there is a 
robustness issue there.

Card type detection (and vacant slot detection) is a good idea but I'm not 
sure how we can detect this chip reliably.

-- 

> 
> Signed-off-by: Ondrej Zary <linux@...nbow-software.org>
> ---
>  drivers/scsi/NCR5380.c |    5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c
> index 01c0027..ce3156d 100644
> --- a/drivers/scsi/NCR5380.c
> +++ b/drivers/scsi/NCR5380.c
> @@ -495,6 +495,11 @@ static int NCR5380_init(struct Scsi_Host *instance, int flags)
>  
>  	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
>  	NCR5380_write(MODE_REG, MR_BASE);
> +	/* check if the chip is really there */
> +	if (NCR5380_read(MODE_REG) != MR_BASE) {
> +		NCR5380_exit(instance);
> +		return -ENODEV;
> +	}
>  	NCR5380_write(TARGET_COMMAND_REG, 0);
>  	NCR5380_write(SELECT_ENABLE_REG, 0);
>  
>