linux-kernel - Re: [PATCH 2/4] Input: synaptics-rmi4 - fix endianness issue in SMBus transport

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Date:   Fri, 31 Mar 2017 11:15:05 +0200
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Andrew Duggan <aduggan@...aptics.com>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, Nick Dyer <nick@...anahar.org>
Subject: Re: [PATCH 2/4] Input: synaptics-rmi4 - fix endianness issue in
 SMBus transport

On Mar 24 2017 or thereabouts, Dmitry Torokhov wrote:
> The mapping table holds address in LE form, so we should convert it
> to CPU when comparing it.

Are you sure about that?

>From what I can read:
rmiaddr is set by rmi_smb_get_command_code(), and it's forwarded
directly from the caller to the table. When we write the data to the
device, we use cpu_to_le16() so rmiaddr is used as le16, but always
stored as CPU type.

> 
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> ---
>  drivers/input/rmi4/rmi_smbus.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/input/rmi4/rmi_smbus.c b/drivers/input/rmi4/rmi_smbus.c
> index 76752555d809..c8bf49686460 100644
> --- a/drivers/input/rmi4/rmi_smbus.c
> +++ b/drivers/input/rmi4/rmi_smbus.c
> @@ -89,17 +89,16 @@ static int rmi_smb_get_command_code(struct rmi_transport_dev *xport,
>  
>  	mutex_lock(&rmi_smb->mappingtable_mutex);
>  	for (i = 0; i < RMI_SMB2_MAP_SIZE; i++) {
> -		if (rmi_smb->mapping_table[i].rmiaddr == rmiaddr) {
> +		struct mapping_table_entry *entry = &rmi_smb->mapping_table[i];

In case you want to keep the temporary variable here, I believe
checkpatch would complain about a missing empty line here (just
nitpicking).

Cheers,
Benjamin

> +		if (le16_to_cpu(entry->rmiaddr) == rmiaddr) {
>  			if (isread) {
> -				if (rmi_smb->mapping_table[i].readcount
> -							== bytecount) {
> +				if (entry->readcount == bytecount) {
>  					*commandcode = i;
>  					retval = 0;
>  					goto exit;
>  				}
>  			} else {
> -				if (rmi_smb->mapping_table[i].flags &
> -							RMI_SMB2_MAP_FLAGS_WE) {
> +				if (entry->flags & RMI_SMB2_MAP_FLAGS_WE) {
>  					*commandcode = i;
>  					retval = 0;
>  					goto exit;
> -- 
> 2.12.1.578.ge9c3154ca4-goog
>