Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754533AbcKBHqA (ORCPT ); Wed, 2 Nov 2016 03:46:00 -0400 Received: from kvm5.telegraphics.com.au ([98.124.60.144]:46066 "EHLO kvm5.telegraphics.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752679AbcKBHp7 (ORCPT ); Wed, 2 Nov 2016 03:45:59 -0400 Date: Wed, 2 Nov 2016 18:46:06 +1100 (AEDT) From: Finn Thain To: Ondrej Zary cc: Christoph Hellwig , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/6] g_NCR5380: Check for chip presence before calling NCR5380_init() In-Reply-To: <1477945112-25659-4-git-send-email-linux@rainbow-software.org> Message-ID: References: <1477945112-25659-1-git-send-email-linux@rainbow-software.org> <1477945112-25659-4-git-send-email-linux@rainbow-software.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1123 Lines: 43 On Mon, 31 Oct 2016, Ondrej Zary wrote: > Write and read back MODE_REG to check if the chip is really there > before doing more initialization. > > This prevents hang when incorrect I/O address was specified by user (in > the most common case where no device is present there so all reads > result in 0xff). > > Signed-off-by: Ondrej Zary > --- > drivers/scsi/g_NCR5380.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/scsi/g_NCR5380.c b/drivers/scsi/g_NCR5380.c > index 0d1f6ad..e713dba 100644 > --- a/drivers/scsi/g_NCR5380.c > +++ b/drivers/scsi/g_NCR5380.c > @@ -322,6 +322,13 @@ static int generic_NCR5380_init_one(struct scsi_host_template *tpnt, > } > } > > + /* check if the chip is really there */ > + NCR5380_write(MODE_REG, 0); > + if (NCR5380_read(MODE_REG) != 0) { Wouldn't it be more accurate to write, /* Check for some kind of device. A vacant slot reads 0xff. */ ? > + ret = -ENODEV; > + goto out_unregister; > + } > + > ret = NCR5380_init(instance, flags | FLAG_LATE_DMA_SETUP); > if (ret) > goto out_unregister; > --