[dm-devel] Re: [PATCH 2/7] scsi_dh: Add 'dh_state' sysfs attribute

[Hannes Reinecke]

Chandra Seetharaman wrote:
> On Wed, 2008-05-14 at 16:43 +0200, Hannes Reinecke wrote:
>> Implement a 'dh_state' sdev attribute for dynamic device handler
>> manipulation. A read on the attribute will return the name of
>> the currently attached device handler or 'detached' if no handler
>> is attached.
>> The attribute allows the following strings to be written:
>> - The name of the device handler to be attached if the state is
>>   'detached'.
>> - 'activate' to trigger path activation if a device handler
>>   is attached.
>> - 'detach' to detach the currently attached device handler.
>>
>> Signed-off-by: Hannes Reinecke <hare at suse.de>
>> ---
> 
> All the sysfs functions can be grouped together. Helps in readability.
> 
?? But I did ... Or thought so, anyway. Checking.

>>  drivers/scsi/device_handler/scsi_dh.c |   88 +++++++++++++++++++++++++++++++++
>>  1 files changed, 88 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/scsi/device_handler/scsi_dh.c b/drivers/scsi/device_handler/scsi_dh.c
>> index 55e5fd2..2dbf84b 100644
>> --- a/drivers/scsi/device_handler/scsi_dh.c
>> +++ b/drivers/scsi/device_handler/scsi_dh.c
>> @@ -54,6 +54,55 @@ static struct scsi_device_handler *get_device_handler(const char *name)
>>  	return found;
>>  }
>>
>> +static ssize_t
>> +store_dh_state(struct device *dev, struct device_attribute *attr,
>> +	       const char *buf, size_t count)
>> +{
>> +	struct scsi_device *sdev = to_scsi_device(dev);
>> +	struct scsi_device_handler *scsi_dh;
>> +	int err = -EINVAL;
>> +
>> +	if (!sdev->scsi_dh_data) {
>> +		/*
>> +		 * Attach to a device handler
>> +		 */ 
>> +		if (!(scsi_dh = get_device_handler(buf)))
>> +			return err;
>> +		err = scsi_dh_handler_attach(sdev, scsi_dh);
>> +	} else {
>> +		/*
>> +		 * Detach from a device handler
>> +		 */
>> +		if (!strncmp(buf, "detach", 6)) {
>> +			err = scsi_dh_handler_detach(sdev);
>> +		} else if (!strncmp(buf, "activate", 8)) {
>> +			scsi_dh = sdev->scsi_dh_data->scsi_dh;
>> +
>> +			err = scsi_dh->activate(sdev);
>> +		}
>> +	}
>> +
>> +	return err<0?err:count;
>> +}
>> +
>> +static ssize_t
>> +show_dh_state(struct device *dev, struct device_attribute *attr, char *buf)
>> +{
>> +	struct scsi_device *sdev = to_scsi_device(dev);
>> +	struct scsi_device_handler *scsi_dh;
>> +
>> +	if (!sdev->scsi_dh_data)
>> +		return snprintf(buf, 20, "detached\n");
>> +
>> +	scsi_dh = sdev->scsi_dh_data->scsi_dh;
> 
> we can use it directly instead of this variable ?
> 
Yes.

>> +
>> +	return snprintf(buf, 20, "%s\n", scsi_dh->name);
>> +}
>> +
>> +static struct device_attribute scsi_dh_state_attr =
>> +	__ATTR(dh_state, S_IRUGO | S_IWUSR, show_dh_state,
>> +	       store_dh_state);
>> +
>>  /*
>>   * scsi_dh_handler_attach - Attach a device handler to a device
>>   * @sdev - SCSI device the device handler should attach to
>> @@ -115,9 +164,11 @@ static int scsi_dh_notifier(struct notifier_block *nb,
>>
>>  	if (action == BUS_NOTIFY_ADD_DEVICE) {
>>  		scsi_dh_handler_attach(sdev, devinfo->handler);
>> +		device_create_file(dev, &scsi_dh_state_attr);
> 
> A later patch checks for the return status of scsi_dh_handler_attach(),
> should be moved here.
> 
Ok.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare at suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)