linux-kernel - Re: [PATCH 01/11] mmc: core: Add helper function to indicate if SDIO IRQs is enabled

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Date:   Wed, 4 Sep 2019 16:58:36 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-mmc@...r.kernel.org, Adrian Hunter <adrian.hunter@...el.com>,
        Douglas Anderson <dianders@...omium.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Yong Mao <yong.mao@...iatek.com>,
        Chaotian Jing <chaotian.jing@...iatek.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/11] mmc: core: Add helper function to indicate if SDIO
 IRQs is enabled

Hi Ulf,

On Tue, Sep 03, 2019 at 04:21:57PM +0200, Ulf Hansson wrote:
> To avoid each host driver supporting SDIO IRQs, from keeping track
> internally about if SDIO IRQs has been enabled, let's introduce a common
> helper function, sdio_irq_enabled().
> 
> The function returns true if SDIO IRQs are enabled, via using the
> information about the number of claimed irqs. This is safe, even without
> any locks, as long as the helper function is called only from
> runtime/system suspend callbacks of the host driver.
> 
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> ---
>  include/linux/mmc/host.h | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 4a351cb7f20f..0c0a565c7ff1 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -493,6 +493,15 @@ void mmc_command_done(struct mmc_host *host, struct mmc_request *mrq);
>  
>  void mmc_cqe_request_done(struct mmc_host *host, struct mmc_request *mrq);
>  
> +/*
> + * May be called from host driver's system/runtime suspend/resume callbacks,
> + * to know if SDIO IRQs has been enabled.
> +*/
> +static inline bool sdio_irq_enabled(struct mmc_host *host)
> +{
> +	return host->sdio_irqs > 0;
> +}
> +

The name of the function is a bit misleadling, since it indicates
if SDIO IRQs should be enabled, not whether they are actually enabled
by the host. The resulting code can look a bit confusing to the
uninstructed reader:

  if (sdio_irq_enabled(host->slot->mmc))
    __dw_mci_enable_sdio_irq(host->slot, 1);

aka 'if SDIO IRQ is enabled, enable SDIO IRQ'.

sdio_irqs_claimed() could be a possible alternative.

No biggie though, just something I noticed.