[v3,07/16] ntb: add check and comment for link up to mw_count() and mw_get_align()

Adds a comment and a check to ntb_mw_get_align() so that it always fails
if the function is called before the link is up.

Also adds a comment to ntb_mw_count() to note that it may return 0 if
it is called before the link is up.

This is to prevent accidental mis-use in clients that are testing
on hardware that this doesn't matter for.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 include/linux/ntb.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

On Tue, Jul 25, 2017 at 02:57:44PM -0600, Logan Gunthorpe wrote:
> Adds a comment and a check to ntb_mw_get_align() so that it always fails
> if the function is called before the link is up.
> 
> Also adds a comment to ntb_mw_count() to note that it may return 0 if
> it is called before the link is up.
> 
> This is to prevent accidental mis-use in clients that are testing
> on hardware that this doesn't matter for.
> 
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>

Similar to the last one, I think this is also a bug fix.  I'll pull it
out, etc.  :)

Thanks,
Jon

> ---
>  include/linux/ntb.h | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/ntb.h b/include/linux/ntb.h
> index 609e232c00da..47f2966cfd7f 100644
> --- a/include/linux/ntb.h
> +++ b/include/linux/ntb.h
> @@ -730,7 +730,8 @@ static inline int ntb_link_disable(struct ntb_dev *ntb)
>   * Hardware and topology may support a different number of memory windows.
>   * Moreover different peer devices can support different number of memory
>   * windows. Simply speaking this method returns the number of possible inbound
> - * memory windows to share with specified peer device.
> + * memory windows to share with specified peer device. Note: this may return
> + * zero if the link is not up yet.
>   *
>   * Return: the number of memory windows.
>   */
> @@ -751,7 +752,7 @@ static inline int ntb_mw_count(struct ntb_dev *ntb, int pidx)
>   * Get the alignments of an inbound memory window with specified index.
>   * NULL may be given for any output parameter if the value is not needed.
>   * The alignment and size parameters may be used for allocation of proper
> - * shared memory.
> + * shared memory. Note: this must only be called when the link is up.
>   *
>   * Return: Zero on success, otherwise a negative error number.
>   */
> @@ -760,6 +761,9 @@ static inline int ntb_mw_get_align(struct ntb_dev *ntb, int pidx, int widx,
>  				   resource_size_t *size_align,
>  				   resource_size_t *size_max)
>  {
> +	if (!(ntb_link_is_up(ntb, NULL, NULL) & (1 << pidx)))
> +		return -ENOTCONN;
> +
>  	return ntb->ops->mw_get_align(ntb, pidx, widx, addr_align, size_align,
>  				      size_max);
>  }
> -- 
> 2.11.0
> 
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