Re: [PATCH v6 16/17] crypto/nx: Add sysfs interface to export NX capabilities

[Nicholas Piggin <npiggin@gmail.com>]

Excerpts from Haren Myneni's message of June 18, 2021 6:39 am:
> 
> Export NX-GZIP capabilities to usrespace in sysfs
> /sys/devices/vio/ibm,compression-v1/nx_gzip_caps directory.
> These are queried by userspace accelerator libraries to set
> minimum length heuristics and maximum limits on request sizes.
> 
> NX-GZIP capabilities:
> min_compress_len  /*Recommended minimum compress length in bytes*/
> min_decompress_len /*Recommended minimum decompress length in bytes*/
> req_max_processed_len /* Maximum number of bytes processed in one
> 			request */
> 
> NX will return RMA_Reject if the request buffer size is greater
> than req_max_processed_len.
> 
> Signed-off-by: Haren Myneni <haren@linux.ibm.com>
> Acked-by: Herbert Xu <herbert@gondor.apana.org.au>

Again, if you could just move those ^^ C style comments into the
code. Possibly have a small comment with the sysfs stuff saying that 
it's ABI which userspace code queries when using the accelerator (or
if you have an ABI documentation somewhere, point the comments to that).

sysfs is ABI, but some bits are more ABI than others, it would just be
good to be clear that it is actually used, and can't be changed.

Aside from that,

Acked-by: Nicholas Piggin <npiggin@gmail.com>

Thanks,
Nick

> ---
>  drivers/crypto/nx/nx-common-pseries.c | 43 +++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> diff --git a/drivers/crypto/nx/nx-common-pseries.c b/drivers/crypto/nx/nx-common-pseries.c
> index 9fc2abb56019..f51a50d40504 100644
> --- a/drivers/crypto/nx/nx-common-pseries.c
> +++ b/drivers/crypto/nx/nx-common-pseries.c
> @@ -967,6 +967,36 @@ static struct attribute_group nx842_attribute_group = {
>  	.attrs = nx842_sysfs_entries,
>  };
>  
> +#define	nxcop_caps_read(_name)						\
> +static ssize_t nxcop_##_name##_show(struct device *dev,			\
> +			struct device_attribute *attr, char *buf)	\
> +{									\
> +	return sprintf(buf, "%lld\n", nx_cop_caps._name);		\
> +}
> +
> +#define NXCT_ATTR_RO(_name)						\
> +	nxcop_caps_read(_name);						\
> +	static struct device_attribute dev_attr_##_name = __ATTR(_name,	\
> +						0444,			\
> +						nxcop_##_name##_show,	\
> +						NULL);
> +
> +NXCT_ATTR_RO(req_max_processed_len);
> +NXCT_ATTR_RO(min_compress_len);
> +NXCT_ATTR_RO(min_decompress_len);
> +
> +static struct attribute *nxcop_caps_sysfs_entries[] = {
> +	&dev_attr_req_max_processed_len.attr,
> +	&dev_attr_min_compress_len.attr,
> +	&dev_attr_min_decompress_len.attr,
> +	NULL,
> +};
> +
> +static struct attribute_group nxcop_caps_attr_group = {
> +	.name	=	"nx_gzip_caps",
> +	.attrs	=	nxcop_caps_sysfs_entries,
> +};
> +
>  static struct nx842_driver nx842_pseries_driver = {
>  	.name =		KBUILD_MODNAME,
>  	.owner =	THIS_MODULE,
> @@ -1056,6 +1086,16 @@ static int nx842_probe(struct vio_dev *viodev,
>  		goto error;
>  	}
>  
> +	if (caps_feat) {
> +		if (sysfs_create_group(&viodev->dev.kobj,
> +					&nxcop_caps_attr_group)) {
> +			dev_err(&viodev->dev,
> +				"Could not create sysfs NX capability entries\n");
> +			ret = -1;
> +			goto error;
> +		}
> +	}
> +
>  	return 0;
>  
>  error_unlock:
> @@ -1075,6 +1115,9 @@ static void nx842_remove(struct vio_dev *viodev)
>  	pr_info("Removing IBM Power 842 compression device\n");
>  	sysfs_remove_group(&viodev->dev.kobj, &nx842_attribute_group);
>  
> +	if (caps_feat)
> +		sysfs_remove_group(&viodev->dev.kobj, &nxcop_caps_attr_group);
> +
>  	crypto_unregister_alg(&nx842_pseries_alg);
>  
>  	spin_lock_irqsave(&devdata_mutex, flags);
> -- 
> 2.18.2
> 
> 
>