Thread (14 messages) 14 messages, 2 authors, 2016-08-19

Re: [PATCH 1/5] i2c: i2c-smbus: prevent races on remove when Host Notify is used

From: Jean Delvare <hidden>
Date: 2016-08-01 13:32:20
Also in: lkml

Hi Benjamin,

On Fri, 29 Jul 2016 11:12:12 +0200, Jean Delvare wrote:
On Thu, 28 Jul 2016 11:50:39 +0200, Benjamin Tissoires wrote:
quoted
+static void i801_disable_host_notify(struct i2c_adapter *adapter)
+{
+	struct i801_priv *priv = i2c_get_adapdata(adapter);
You pass the adapter as the parameter, but don't need it. All you need
is priv, which the caller has too. So you could pass priv as the
parameter directly and avoid the glue code.
quoted
+
+	if (!(priv->features & FEATURE_HOST_NOTIFY))
+		return;
+
+	/* disable Host Notify... */
+	outb_p(0, SMBSLVCMD(priv));
This assumes there's only one bit in the register, which is not true.
There are 3 bits. I did not notice the problem during my original
review, but in i801_enable_host_notify() you are silently zero-ing the
other 2 bits too, which isn't nice. You should only touch the bit that
matters to you, both here and in i801_enable_host_notify().
Thinking about it some more, I'd like to add: what if host notify was
enabled before the driver was loaded? The driver should leave the
controller in the same state it found it, ideally. We have learned in
the past that doing otherwise for PEC and I2C mode, for example, leads
to problems (lock-up on shutdown) on some systems.

This could happen with Host Notify as well. So I think you should save
the value at driver load time and restore it at unload time (same we do
with the hstcfg register.)

-- 
Jean Delvare
SUSE L3 Support
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