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SubjectRe: [PATCH 27/29] mfd-core: add refcounting support to mfd_cells (v2)
Hi Andres,

On Thu, Feb 17, 2011 at 07:07:34PM -0800, Andres Salomon wrote:
> This provides convenience functions for sharing of cells across
> multiple mfd clients. Mfd drivers can provide enable/disable hooks
> to actually tweak the hardware, and clients can call
> mfd_shared_cell_{en,dis}able without having to worry about whether
> or not another client happens to have enabled or disabled the
> cell/hardware.
>
> Note that this is purely optional; drivers can continue to use
> the mfd_cell's enable/disable hooks for their own purposes, if
> desired.
>
> v2: modify mfd_shared_cell_enable/disable to only modify refcount
> if the hook call succeeds.
>
> Signed-off-by: Andres Salomon <dilinger@queued.net>
> ---
> drivers/mfd/mfd-core.c | 64 +++++++++++++++++++++++++++++++++++++++++++---
> include/linux/mfd/core.h | 14 +++++++++-
> 2 files changed, 73 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> index 01115f6..ca789f8 100644
> --- a/drivers/mfd/mfd-core.c
> +++ b/drivers/mfd/mfd-core.c
> @@ -18,6 +18,43 @@
> #include <linux/pm_runtime.h>
> #include <linux/slab.h>
>
> +int mfd_shared_cell_enable(struct platform_device *pdev)
> +{
> + const struct mfd_cell *cell = mfd_get_cell(pdev);
> + int err = 0;
> +
> + /* only call enable hook if the cell wasn't previously enabled */
> + if (atomic_inc_return(cell->usage_count) == 1)
> + err = cell->enable(pdev);
> +
> + /* if the enable hook failed, decrement counter to allow retries */
> + if (err)
> + atomic_dec(cell->usage_count);
> +
> + return err;
> +}
> +EXPORT_SYMBOL(mfd_shared_cell_enable);
> +
> +int mfd_shared_cell_disable(struct platform_device *pdev)
> +{
> + const struct mfd_cell *cell = mfd_get_cell(pdev);
> + int err = 0;
> +
> + /* only disable if no other clients are using it */
> + if (atomic_dec_return(cell->usage_count) == 0)
> + err = cell->disable(pdev);
> +
> + /* if the disable hook failed, increment to allow retries */
> + if (err)
> + atomic_inc(cell->usage_count);
> +
> + /* sanity check; did someone call disable too many times? */
> + WARN_ON(atomic_read(cell->usage_count) < 0);
> +
> + return err;
> +}
> +EXPORT_SYMBOL(mfd_shared_cell_disable);
It would probably make sense to rename both of these routines by simply
removing the shared part: mfd_cell_enable/disable().

Cheers,
Samuel.

--
Intel Open Source Technology Centre
http://oss.intel.com/


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