Re: [PATCH 26/39] fireworks: Add command/response functionality into hwdep interface

[Takashi Iwai <tiwai@suse.de>]

At Fri, 28 Feb 2014 12:27:39 +0900,
Takashi Sakamoto wrote:
> 
> This commit adds two functionality for hwdep interface, adds two parameters for
> this driver, add a node for proc interface.
> 
> To receive responses from devices, this driver already allocate own callback
> into private address area in host controller. This means no one can allocate
> its own callback to the address. So this driver must give a way for user
> applications to receive responses.
> 
> This commit adds a functionality to receive responses via hwdep interface. The
> application can receive responses to read from this interface. To achieve this,
> this commit adds a buffer to queue responses. The default size of this buffer is
> 1024 bytes. This size can be changed to give preferrable size to
> 'resp_buf_size' parameter for this driver. The application should notice rest
> of space in this buffer because this driver don't push responses when this
> buffer has no space.
> 
> Additionaly, this commit adds a functionality to transmit commands via hwdep
> interface. The application can transmit commands to write into this interface.
> I note that the application can transmit one command at once, but can receive
> as many responses as possible untill the user-buffer is full.
> 
> When using these interfaces, the application must keep maximum number of
> sequence number in command within the number in firewire.h because this driver
> uses this number to distinguish the response is against the command by the
> application or this driver.
> 
> Usually responses against commands which the application transmits are pushed
> into this buffer. But to enable 'resp_buf_debug' parameter for this driver, all
> responses are pushed into the buffer. When using this mode, I reccomend to
> expand the size of buffer.
> 
> Finally this commit adds a new node into proc interface to output status of the
> buffer.
> 
> Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
> ---
>  include/uapi/sound/firewire.h                    |  18 +++
>  sound/firewire/fireworks/fireworks.c             |  17 +++
>  sound/firewire/fireworks/fireworks.h             |  22 +--
>  sound/firewire/fireworks/fireworks_command.c     |   6 +-
>  sound/firewire/fireworks/fireworks_hwdep.c       | 129 ++++++++++++++---
>  sound/firewire/fireworks/fireworks_proc.c        |  19 +++
>  sound/firewire/fireworks/fireworks_transaction.c | 176 ++++++++++++++++++++---
>  7 files changed, 340 insertions(+), 47 deletions(-)
> 
> diff --git a/include/uapi/sound/firewire.h b/include/uapi/sound/firewire.h
> index fc9afb2..7f4c419 100644
> --- a/include/uapi/sound/firewire.h
> +++ b/include/uapi/sound/firewire.h
> @@ -7,6 +7,7 @@
>  
>  #define SNDRV_FIREWIRE_EVENT_LOCK_STATUS	0x000010cc
>  #define SNDRV_FIREWIRE_EVENT_DICE_NOTIFICATION	0xd1ce004e
> +#define SNDRV_FIREWIRE_EVENT_EFW_RESPONSE	0x4e617475
>  
>  struct snd_firewire_event_common {
>  	unsigned int type; /* SNDRV_FIREWIRE_EVENT_xxx */
> @@ -22,10 +23,27 @@ struct snd_firewire_event_dice_notification {
>  	unsigned int notification; /* DICE-specific bits */
>  };
>  
> +#define SND_EFW_TRANSACTION_SEQNUM_MAX	((uint32_t)(BIT(28) - 1))
> +/* each field should be in big endian */
> +struct snd_efw_transaction {
> +	uint32_t length;
> +	uint32_t version;
> +	uint32_t seqnum;
> +	uint32_t category;
> +	uint32_t command;
> +	uint32_t status;
> +	uint32_t params[0];
> +};
> +struct snd_firewire_event_efw_response {
> +	unsigned int type;
> +	uint32_t response[0];	/* some responses */
> +};
> +
>  union snd_firewire_event {
>  	struct snd_firewire_event_common            common;
>  	struct snd_firewire_event_lock_status       lock_status;
>  	struct snd_firewire_event_dice_notification dice_notification;
> +	struct snd_firewire_event_efw_response      efw_response;
>  };
>  
>  
> diff --git a/sound/firewire/fireworks/fireworks.c b/sound/firewire/fireworks/fireworks.c
> index 38986c0..7846285 100644
> --- a/sound/firewire/fireworks/fireworks.c
> +++ b/sound/firewire/fireworks/fireworks.c
> @@ -24,6 +24,8 @@ MODULE_LICENSE("GPL v2");
>  static int index[SNDRV_CARDS]	= SNDRV_DEFAULT_IDX;
>  static char *id[SNDRV_CARDS]	= SNDRV_DEFAULT_STR;
>  static bool enable[SNDRV_CARDS]	= SNDRV_DEFAULT_ENABLE_PNP;
> +unsigned int resp_buf_size	= 1024;
> +bool resp_buf_debug		= false;
>  
>  module_param_array(index, int, NULL, 0444);
>  MODULE_PARM_DESC(index, "card index");
> @@ -31,6 +33,10 @@ module_param_array(id, charp, NULL, 0444);
>  MODULE_PARM_DESC(id, "ID string");
>  module_param_array(enable, bool, NULL, 0444);
>  MODULE_PARM_DESC(enable, "enable Fireworks sound card");
> +module_param(resp_buf_size, uint, 0444);
> +MODULE_PARM_DESC(resp_buf_size, "response buffer size (default 1024)");
> +module_param(resp_buf_debug, bool, 0444);
> +MODULE_PARM_DESC(resp_buf_debug, "store all responses to buffer");
>  
>  static DEFINE_MUTEX(devices_mutex);
>  static unsigned int devices_used;
> @@ -165,6 +171,7 @@ efw_probe(struct fw_unit *unit,
>  {
>  	struct snd_card *card;
>  	struct snd_efw *efw;
> +	void *resp_buf;
>  	int card_index, err;
>  
>  	mutex_lock(&devices_mutex);
> @@ -178,6 +185,13 @@ efw_probe(struct fw_unit *unit,
>  		goto end;
>  	}
>  
> +	/* prepare response buffer */
> +	resp_buf = kzalloc(resp_buf_size, GFP_KERNEL);

Better to have a sanity check of resp_buf_size value.  You can't trust
a value given by a user.


Takashi