[PATCH linux dev-4.7] drivers: fsi: Fix incremeting dev nums

[Jeremy Kerr]

Hi Eddie,

> From: "Edward A. James" <eajames at us.ibm.com>
> 
> both for FSI master and scom client
> 
> Signed-off-by: Edward A. James <eajames at us.ibm.com>
> ---
>  drivers/fsi/fsi-core.c | 4 +++-
>  drivers/fsi/fsi-scom.c | 2 ++
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
> index e8a3618..7816482 100644
> --- a/drivers/fsi/fsi-core.c
> +++ b/drivers/fsi/fsi-core.c
> @@ -46,7 +46,7 @@ static const int engine_page_size = 0x400;
>  static struct task_struct *master_ipoll;
>  static unsigned int fsi_ipoll_period_ms = 100;
>  
> -static atomic_t master_idx = ATOMIC_INIT(-1);
> +static atomic_t master_idx = ATOMIC_INIT(0);

This will mean that our first master is numbered 1 instead of zero. Not
a huge problem, but it doesn't sound like that's what you wanted to do
here.

>  struct fsi_slave {
>  	struct list_head	list_link;	/* Master's list of slaves */
> @@ -617,6 +617,8 @@ void fsi_master_unregister(struct fsi_master *master)
>  		kthread_stop(master_ipoll);
>  		master_ipoll = NULL;
>  	}
> +
> +	atomic_dec(&master_idx);

This doesn't work. Consider (starting from -1):

  - master_idx at -1
  - master added, assigned index 0, master_idx now at 0
  - master added, assigned index 1, master idx now at 1
  - master 0 removed, master_idx now at 0
  - master added, assigned index 1

now we have two masters with index 1.

Either we need to check for present masters, or use the ida functions
(as greg kh has suggested).

So, nak from me on this.

Regards,


Jeremy