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Message-ID: <c87a9702-07c3-412f-a9a9-0e32b8aab668@gmail.com>
Date: Thu, 21 Mar 2024 17:11:20 +0100
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Subject: Re: [PATCH] i2c: i801: Fix a refactoring that broke a touchpad on
 Lenovo P1
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To: Maxim Levitsky <mlevitsk@redhat.com>, Jean Delvare <jdelvare@suse.com>,
 Andi Shyti <andi.shyti@kernel.org>
Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20240321141919.26844-1-mlevitsk@redhat.com>
From: Heiner Kallweit <hkallweit1@gmail.com>
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In-Reply-To: <20240321141919.26844-1-mlevitsk@redhat.com>
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On 21.03.2024 15:19, Maxim Levitsky wrote:
> Commit 857cc04cdf50 ("i2c: i801: Add helper i801_get_block_len")
> introduced a slight functional change: the status variable is now
> overwritten with the length of an SMBUS tranasaction,
> even in case of success.
> 
> This breaks the touchpad on at least my Lenovo P1:
> 
> rmi4_physical rmi4-00: Read PDT entry at 0x00e9 failed, code: -6.
> rmi4_physical rmi4-00: RMI initial reset failed! Continuing in spite of this.
> rmi4_physical rmi4-00: Read PDT entry at 0x00e9 failed, code: -6.
> rmi4_physical rmi4-00: IRQ counting failed with code -6.
> 
> Fixes: 857cc04cdf50 ("i2c: i801: Add helper i801_get_block_len")
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  drivers/i2c/busses/i2c-i801.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index a6861660cb8c..79870dd7a014 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -536,11 +536,12 @@ static int i801_block_transaction_by_block(struct i801_priv *priv,
>  
>  	if (read_write == I2C_SMBUS_READ ||
>  	    command == I2C_SMBUS_BLOCK_PROC_CALL) {
> -		status = i801_get_block_len(priv);
> -		if (status < 0)
> +		len = i801_get_block_len(priv);
> +		if (len < 0) {
> +			status = len;
>  			goto out;
> +		}
>  
> -		len = status;
>  		data->block[0] = len;
>  		inb_p(SMBHSTCNT(priv));	/* reset the data buffer index */
>  		for (i = 0; i < len; i++)

Indeed, my bad.

Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com>