linux-kernel - [PATCH 3/6] g_NCR5380: Check for chip presence before calling NCR5380

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Date:   Mon, 31 Oct 2016 21:18:29 +0100
From:   Ondrej Zary <linux@...nbow-software.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Finn Thain <fthain@...egraphics.com.au>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/6] g_NCR5380: Check for chip presence before calling NCR5380_init()

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 <linux@...nbow-software.org>
---
 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) {
+		ret = -ENODEV;
+		goto out_unregister;
+	}
+
 	ret = NCR5380_init(instance, flags | FLAG_LATE_DMA_SETUP);
 	if (ret)
 		goto out_unregister;
-- 
Ondrej Zary