[PATCH][next] tty: serial: jsm: remove redundant assignments of several variables

[PATCH][next] tty: serial: jsm: remove redundant assignments of several variables

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

Several variables are being assigned with values that are never
read and being updated later with a new value. The initializations
are redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/tty/serial/jsm/jsm_cls.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/jsm/jsm_cls.c b/drivers/tty/serial/jsm/jsm_cls.c
index b507a2cec926..b58ea4344aaf 100644
--- a/drivers/tty/serial/jsm/jsm_cls.c
+++ b/drivers/tty/serial/jsm/jsm_cls.c
@@ -349,8 +349,8 @@ static void cls_assert_modem_signals(struct jsm_channel *ch)
 
 static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
 {
-	int qleft = 0;
-	u8 linestatus = 0;
+	int qleft;
+	u8 linestatus;
 	u8 error_mask = 0;
 	u16 head;
 	u16 tail;
@@ -365,8 +365,6 @@ static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
 	head = ch->ch_r_head & RQUEUEMASK;
 	tail = ch->ch_r_tail & RQUEUEMASK;
 
-	/* Get our cached LSR */
-	linestatus = ch->ch_cached_lsr;
 	ch->ch_cached_lsr = 0;
 
 	/* Store how much space we have left in the queue */
-- 
2.30.2

Re: [PATCH][next] tty: serial: jsm: remove redundant assignments of several variables

[Johan Hovold]

On Thu, Apr 22, 2021 at 01:11:15PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Several variables are being assigned with values that are never
> read and being updated later with a new value. The initializations
> are redundant and can be removed.
> 
> Addresses-Coverity: ("Unused value")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/tty/serial/jsm/jsm_cls.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/jsm/jsm_cls.c b/drivers/tty/serial/jsm/jsm_cls.c
> index b507a2cec926..b58ea4344aaf 100644
> --- a/drivers/tty/serial/jsm/jsm_cls.c
> +++ b/drivers/tty/serial/jsm/jsm_cls.c
> @@ -349,8 +349,8 @@ static void cls_assert_modem_signals(struct jsm_channel *ch)
>  
>  static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
>  {
> -	int qleft = 0;
> -	u8 linestatus = 0;
> +	int qleft;
> +	u8 linestatus;
>  	u8 error_mask = 0;
>  	u16 head;
>  	u16 tail;
> @@ -365,8 +365,6 @@ static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
>  	head = ch->ch_r_head & RQUEUEMASK;
>  	tail = ch->ch_r_tail & RQUEUEMASK;
>  
> -	/* Get our cached LSR */
> -	linestatus = ch->ch_cached_lsr;
>  	ch->ch_cached_lsr = 0;

Why leave this assignment in? Looks like this was all copy-pasta, but
this assignment makes even less sense now that you remove the comment
and load.

Johan

Re: [PATCH][next] tty: serial: jsm: remove redundant assignments of several variables

[Colin Ian King]

On 22/04/2021 13:52, Johan Hovold wrote:
> On Thu, Apr 22, 2021 at 01:11:15PM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> Several variables are being assigned with values that are never
>> read and being updated later with a new value. The initializations
>> are redundant and can be removed.
>>
>> Addresses-Coverity: ("Unused value")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>>  drivers/tty/serial/jsm/jsm_cls.c | 6 ++----
>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/tty/serial/jsm/jsm_cls.c b/drivers/tty/serial/jsm/jsm_cls.c
>> index b507a2cec926..b58ea4344aaf 100644
>> --- a/drivers/tty/serial/jsm/jsm_cls.c
>> +++ b/drivers/tty/serial/jsm/jsm_cls.c
>> @@ -349,8 +349,8 @@ static void cls_assert_modem_signals(struct jsm_channel *ch)
>>  
>>  static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
>>  {
>> -	int qleft = 0;
>> -	u8 linestatus = 0;
>> +	int qleft;
>> +	u8 linestatus;
>>  	u8 error_mask = 0;
>>  	u16 head;
>>  	u16 tail;
>> @@ -365,8 +365,6 @@ static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
>>  	head = ch->ch_r_head & RQUEUEMASK;
>>  	tail = ch->ch_r_tail & RQUEUEMASK;
>>  
>> -	/* Get our cached LSR */
>> -	linestatus = ch->ch_cached_lsr;
>>  	ch->ch_cached_lsr = 0;
> 
> Why leave this assignment in? Looks like this was all copy-pasta, but
> this assignment makes even less sense now that you remove the comment
> and load.

Which assignment are you referring to?

> 
> Johan
> 

Re: [PATCH][next] tty: serial: jsm: remove redundant assignments of several variables

[Johan Hovold]

On Thu, Apr 22, 2021 at 01:53:03PM +0100, Colin Ian King wrote:
> On 22/04/2021 13:52, Johan Hovold wrote:
> > On Thu, Apr 22, 2021 at 01:11:15PM +0100, Colin King wrote:
> >> From: Colin Ian King <colin.king@canonical.com>
> >>
> >> Several variables are being assigned with values that are never
> >> read and being updated later with a new value. The initializations
> >> are redundant and can be removed.
> >>
> >> Addresses-Coverity: ("Unused value")
> >> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >> ---
> >>  drivers/tty/serial/jsm/jsm_cls.c | 6 ++----
> >>  1 file changed, 2 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/tty/serial/jsm/jsm_cls.c b/drivers/tty/serial/jsm/jsm_cls.c
> >> index b507a2cec926..b58ea4344aaf 100644
> >> --- a/drivers/tty/serial/jsm/jsm_cls.c
> >> +++ b/drivers/tty/serial/jsm/jsm_cls.c
> >> @@ -349,8 +349,8 @@ static void cls_assert_modem_signals(struct jsm_channel *ch)
> >>  
> >>  static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
> >>  {
> >> -	int qleft = 0;
> >> -	u8 linestatus = 0;
> >> +	int qleft;
> >> +	u8 linestatus;
> >>  	u8 error_mask = 0;
> >>  	u16 head;
> >>  	u16 tail;
> >> @@ -365,8 +365,6 @@ static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
> >>  	head = ch->ch_r_head & RQUEUEMASK;
> >>  	tail = ch->ch_r_tail & RQUEUEMASK;
> >>  
> >> -	/* Get our cached LSR */
> >> -	linestatus = ch->ch_cached_lsr;
> >>  	ch->ch_cached_lsr = 0;
> > 
> > Why leave this assignment in? Looks like this was all copy-pasta, but
> > this assignment makes even less sense now that you remove the comment
> > and load.
> 
> Which assignment are you referring to?

The one just above my comment: 

	ch->ch_cached_lsr = 0;

Johan

Re: [PATCH][next] tty: serial: jsm: remove redundant assignments of several variables

[Colin Ian King]

On 22/04/2021 13:56, Johan Hovold wrote:
> On Thu, Apr 22, 2021 at 01:53:03PM +0100, Colin Ian King wrote:
>> On 22/04/2021 13:52, Johan Hovold wrote:
>>> On Thu, Apr 22, 2021 at 01:11:15PM +0100, Colin King wrote:
>>>> From: Colin Ian King <colin.king@canonical.com>
>>>>
>>>> Several variables are being assigned with values that are never
>>>> read and being updated later with a new value. The initializations
>>>> are redundant and can be removed.
>>>>
>>>> Addresses-Coverity: ("Unused value")
>>>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>>>> ---
>>>>  drivers/tty/serial/jsm/jsm_cls.c | 6 ++----
>>>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/tty/serial/jsm/jsm_cls.c b/drivers/tty/serial/jsm/jsm_cls.c
>>>> index b507a2cec926..b58ea4344aaf 100644
>>>> --- a/drivers/tty/serial/jsm/jsm_cls.c
>>>> +++ b/drivers/tty/serial/jsm/jsm_cls.c
>>>> @@ -349,8 +349,8 @@ static void cls_assert_modem_signals(struct jsm_channel *ch)
>>>>  
>>>>  static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
>>>>  {
>>>> -	int qleft = 0;
>>>> -	u8 linestatus = 0;
>>>> +	int qleft;
>>>> +	u8 linestatus;
>>>>  	u8 error_mask = 0;
>>>>  	u16 head;
>>>>  	u16 tail;
>>>> @@ -365,8 +365,6 @@ static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
>>>>  	head = ch->ch_r_head & RQUEUEMASK;
>>>>  	tail = ch->ch_r_tail & RQUEUEMASK;
>>>>  
>>>> -	/* Get our cached LSR */
>>>> -	linestatus = ch->ch_cached_lsr;
>>>>  	ch->ch_cached_lsr = 0;
>>>
>>> Why leave this assignment in? Looks like this was all copy-pasta, but
>>> this assignment makes even less sense now that you remove the comment
>>> and load.
>>
>> Which assignment are you referring to?
> 
> The one just above my comment: 
> 
> 	ch->ch_cached_lsr = 0;

that cached value is being used in jsm_neo.c, so removing the zero'ing
may cause some issues.

> 
> Johan
> 

Re: [PATCH][next] tty: serial: jsm: remove redundant assignments of several variables

[Johan Hovold]

On Thu, Apr 22, 2021 at 02:01:36PM +0100, Colin Ian King wrote:
> On 22/04/2021 13:56, Johan Hovold wrote:
> > On Thu, Apr 22, 2021 at 01:53:03PM +0100, Colin Ian King wrote:
> >> On 22/04/2021 13:52, Johan Hovold wrote:
> >>> On Thu, Apr 22, 2021 at 01:11:15PM +0100, Colin King wrote:
> >>>> From: Colin Ian King <colin.king@canonical.com>
> >>>>
> >>>> Several variables are being assigned with values that are never
> >>>> read and being updated later with a new value. The initializations
> >>>> are redundant and can be removed.
> >>>>
> >>>> Addresses-Coverity: ("Unused value")
> >>>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >>>> ---
> >>>>  drivers/tty/serial/jsm/jsm_cls.c | 6 ++----
> >>>>  1 file changed, 2 insertions(+), 4 deletions(-)
> >>>>
> >>>> diff --git a/drivers/tty/serial/jsm/jsm_cls.c b/drivers/tty/serial/jsm/jsm_cls.c
> >>>> index b507a2cec926..b58ea4344aaf 100644
> >>>> --- a/drivers/tty/serial/jsm/jsm_cls.c
> >>>> +++ b/drivers/tty/serial/jsm/jsm_cls.c
> >>>> @@ -349,8 +349,8 @@ static void cls_assert_modem_signals(struct jsm_channel *ch)
> >>>>  
> >>>>  static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
> >>>>  {
> >>>> -	int qleft = 0;
> >>>> -	u8 linestatus = 0;
> >>>> +	int qleft;
> >>>> +	u8 linestatus;
> >>>>  	u8 error_mask = 0;
> >>>>  	u16 head;
> >>>>  	u16 tail;
> >>>> @@ -365,8 +365,6 @@ static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
> >>>>  	head = ch->ch_r_head & RQUEUEMASK;
> >>>>  	tail = ch->ch_r_tail & RQUEUEMASK;
> >>>>  
> >>>> -	/* Get our cached LSR */
> >>>> -	linestatus = ch->ch_cached_lsr;
> >>>>  	ch->ch_cached_lsr = 0;
> >>>
> >>> Why leave this assignment in? Looks like this was all copy-pasta, but
> >>> this assignment makes even less sense now that you remove the comment
> >>> and load.
> >>
> >> Which assignment are you referring to?
> > 
> > The one just above my comment: 
> > 
> > 	ch->ch_cached_lsr = 0;
> 
> that cached value is being used in jsm_neo.c, so removing the zero'ing
> may cause some issues.

That's for you to determine, right? Only doing half of a clean may
actually be worse than doing nothing at all. At least now it's somewhat
clear why that statement is there.

The jsm_neo.c implements support for a different class of devices and
only those actually use ch_cached_lsr AFAICT.

It would be good if you include some context in the commit message such
as which commit added this code and that it has never been used.

Johan