linux-kernel - Re: [PATCH v5 2/5] firmware: encapsulate firmware loading status

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Date:   Tue, 13 Sep 2016 11:47:08 +0200
From:   Daniel Wagner <daniel.wagner@...-carit.de>
To:     "Luis R . Rodriguez" <mcgrof@...nel.org>
CC:     Daniel Wagner <wagi@...om.org>, <linux-kernel@...r.kernel.org>,
        Ming Lei <ming.lei@...onical.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Srivatsa S . Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
        "Rafael J . Wysocki" <rjw@...k.pl>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Takashi Iwai <tiwai@...e.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Arend van Spriel <arend.vanspriel@...adcom.com>
Subject: Re: [PATCH v5 2/5] firmware: encapsulate firmware loading status

Hi Luis,


On 09/09/2016 02:12 PM, Daniel Wagner wrote:
> The firmware user helper code tracks the current state of the loading
> process via unsigned long status and a complection in struct
> firmware_buf. We only need this for the usermode helper as such we can
> encapsulate all this data into its own data structure.

I don't think we are able to move the completion code into a 
CONFIG_FW_LOADER_HELPER section. The direct loading path uses completion 
as well.

> +#ifdef CONFIG_FW_LOADER_USER_HELPER
> +
> +enum {
> +	FW_UMH_UNKNOWN,
> +	FW_UMH_LOADING,
> +	FW_UMH_DONE,
> +	FW_UMH_ABORTED,
> +};

The direct loading path just uses two states, LOADING and DONE. ABORTED 
is not used.

> +struct fw_umh {
> +	struct completion completion;
> +	unsigned long status;
> +};
> +
> +static void fw_umh_init(struct fw_umh *fw_umh)
> +{
> +	init_completion(&fw_umh->completion);
> +	fw_umh->status = FW_UMH_UNKNOWN;
> +}
> +
> +static int __fw_umh_check(struct fw_umh *fw_umh, unsigned long status)
> +{
> +	return test_bit(status, &fw_umh->status);
> +}
> +
> +static int fw_umh_wait_timeout(struct fw_umh *fw_umh, long timeout)
> +{
> +	int ret;
> +
> +	ret = wait_for_completion_interruptible_timeout(&fw_umh->completion,
> +							timeout);
> +	if (ret != 0 && test_bit(FW_UMH_ABORTED, &fw_umh->status))
> +		return -ENOENT;
> +
> +	return ret;
> +}
> +
> +static void __fw_umh_set(struct fw_umh *fw_umh,
> +			  unsigned long status)
> +{
> +	set_bit(status, &fw_umh->status);
> +
> +	if (status == FW_UMH_DONE || status == FW_UMH_ABORTED) {
> +		clear_bit(FW_UMH_LOADING, &fw_umh->status);
> +		complete_all(&fw_umh->completion);
> +	}
> +}
> +
> +#define fw_umh_start(fw_umh)					\
> +	__fw_umh_set(fw_umh, FW_UMH_LOADING)
> +#define fw_umh_done(fw_umh)					\
> +	__fw_umh_set(fw_umh, FW_UMH_DONE)
> +#define fw_umh_aborted(fw_umh)					\
> +	__fw_umh_set(fw_umh, FW_UMH_ABORTED)
> +#define fw_umh_is_loading(fw_umh)				\
> +	__fw_umh_check(fw_umh, FW_UMH_LOADING)
> +#define fw_umh_is_done(fw_umh)					\
> +	__fw_umh_check(fw_umh, FW_UMH_DONE)
> +#define fw_umh_is_aborted(fw_umh)				\
> +	__fw_umh_check(fw_umh, FW_UMH_ABORTED)
> +
> +#else /* CONFIG_FW_LOADER_USER_HELPER */
> +
> +#define fw_umh_wait_timeout(fw_st, long)	0
> +
> +#define fw_umh_done(fw_st)
> +#define fw_umh_is_done(fw_st)			true
> +#define fw_umh_is_aborted(fw_st)		false

We still need the implementation for fw_umh_wait_timeout() and 
fw_umh_start(), fw_umh_done() etc. fw_umh_is_aborted() is not needed.


> @@ -309,8 +373,7 @@ static void fw_finish_direct_load(struct device *device,
>  				  struct firmware_buf *buf)
>  {
>  	mutex_lock(&fw_lock);
> -	set_bit(FW_STATUS_DONE, &buf->status);
> -	complete_all(&buf->completion);
> +	fw_umh_done(&buf->fw_umh);
>  	mutex_unlock(&fw_lock);
>  }

Here we signal that we have loaded the firmware

>  /* wait until the shared firmware_buf becomes ready (or error) */
>  static int sync_cached_firmware_buf(struct firmware_buf *buf)
>  {
>  	int ret = 0;
>
>  	mutex_lock(&fw_lock);
> -	while (!test_bit(FW_STATUS_DONE, &buf->status)) {
> -		if (is_fw_load_aborted(buf)) {
> +	while (!fw_umh_is_done(&buf->fw_umh)) {
> +		if (fw_umh_is_aborted(&buf->fw_umh)) {
>  			ret = -ENOENT;
>  			break;
>  		}
>  		mutex_unlock(&fw_lock);
> -		ret = wait_for_completion_interruptible(&buf->completion);
> +		ret = fw_umh_wait_timeout(&buf->fw_umh, 0);
>  		mutex_lock(&fw_lock);
>  	}

and here we here we wait for it.

So I suggest to rename it back to fw_status_ and don't move it inside a 
CONFIG_FW_LOADER_HELPER section. Drop the special handling of the 
ABORTED and add instead a comment that the ABORTED state is not used for 
direct loading. This special handling makes unnecessary more complex. 
This is a slowpath and this micro optimization is helping to maintain 
the code.

cheers,
daniel