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Date:   Fri, 17 Feb 2017 09:04:59 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        linux-pci@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        nsekhar@...com
Subject: Re: [PATCH v2 03/22] PCI: endpoint: Introduce configfs entry for
 configuring EP functions

On Fri, Feb 17, 2017 at 03:20:23PM +0530, Kishon Vijay Abraham I wrote:
> Introduce a new configfs entry to configure the EP function (like
> configuring the standard configuration header entries) and to
> bind the EP function with EP controller.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  drivers/pci/endpoint/Kconfig      |   14 +-
>  drivers/pci/endpoint/Makefile     |    1 +
>  drivers/pci/endpoint/pci-ep-cfs.c |  427 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 440 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/pci/endpoint/pci-ep-cfs.c
> 
> diff --git a/drivers/pci/endpoint/Kconfig b/drivers/pci/endpoint/Kconfig
> index 7eb1c79..8470f0b 100644
> --- a/drivers/pci/endpoint/Kconfig
> +++ b/drivers/pci/endpoint/Kconfig
> @@ -6,7 +6,6 @@ menu "PCI Endpoint"
>  
>  config PCI_ENDPOINT
>  	bool "PCI Endpoint Support"
> -	select CONFIGFS_FS
>  	help
>  	   Enable this configuration option to support configurable PCI
>  	   endpoint. This should be enabled if the platform has a PCI
> @@ -14,8 +13,19 @@ config PCI_ENDPOINT
>  
>  	   Enabling this option will build the endpoint library, which
>  	   includes endpoint controller library and endpoint function
> -	   library.
> +	   library. This will also enable the configfs entry required to
> +	   configure the endpoint function and used to bind the
> +	   function with a endpoint controller.
>  
>  	   If in doubt, say "N" to disable Endpoint support.
>  
> +config PCI_ENDPOINT_CONFIGFS
> +	bool "PCI Endpoint Configfs Support"
> +	depends on PCI_ENDPOINT
> +	select CONFIGFS_FS
> +	help
> +	   This will enable the configfs entry that can be used to
> +	   configure the endpoint function and used to bind the
> +	   function with a endpoint controller.
> +
>  endmenu
> diff --git a/drivers/pci/endpoint/Makefile b/drivers/pci/endpoint/Makefile
> index dc1bc16..dd9163c 100644
> --- a/drivers/pci/endpoint/Makefile
> +++ b/drivers/pci/endpoint/Makefile
> @@ -4,3 +4,4 @@
>  
>  obj-$(CONFIG_PCI_ENDPOINT)		+= pci-epc-core.o pci-epf-core.o\
>  					   pci-epc-mem.o
> +obj-$(CONFIG_PCI_ENDPOINT_CONFIGFS)	+= pci-ep-cfs.o
> diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
> new file mode 100644
> index 0000000..ed0f8c2
> --- /dev/null
> +++ b/drivers/pci/endpoint/pci-ep-cfs.c
> @@ -0,0 +1,427 @@
> +/**
> + * configfs to configure the PCI endpoint
> + *
> + * Copyright (C) 2017 Texas Instruments
> + * Author: Kishon Vijay Abraham I <kishon@...com>
> + *
> + * This program is free software: you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 of
> + * the License as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/configfs.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +
> +#include <linux/pci-epc.h>
> +#include <linux/pci-epf.h>
> +
> +struct pci_epf_info {
> +	struct config_group group;
> +	struct list_head list;
> +	struct pci_epf *epf;
> +};
> +
> +struct pci_ep_info {
> +	struct config_group group;
> +	struct config_group pci_epf_group;
> +	/* mutex to protect pci_epf list */
> +	struct mutex lock;
> +	struct list_head pci_epf;
> +	const char *epc_name;
> +	struct pci_epc *epc;
> +};
> +
> +static inline struct pci_epf_info *to_pci_epf_info(struct config_item *item)
> +{
> +	return container_of(to_config_group(item), struct pci_epf_info, group);
> +}
> +
> +static inline struct pci_ep_info *to_pci_ep_info(struct config_item *item)
> +{
> +	return container_of(to_config_group(item), struct pci_ep_info, group);
> +}
> +
> +#define PCI_EPF_HEADER_R(_name)						       \
> +static ssize_t pci_epf_##_name##_show(struct config_item *item,	char *page)    \
> +{									       \
> +	struct pci_epf *epf = to_pci_epf_info(item)->epf;		       \
> +	if (!epf->header) {						       \
> +		WARN_ON_ONCE("epf device not bound to function driver\n");     \

WARN_ON_ONCE takes a string to evaluate as argument, not a message

> +		return 0;					

and if we return 0 here the callers will retry because that is
interpreted as a short read.  The code should be something like:

	if (WARN_ON_ONCE(!epf->header))
		return -EINVAL;

> +	if (!epf->header) {						       \
> +		WARN_ON_ONCE("epf device not bound to function driver\n");     \
> +		return 0;						       \
> +	}								       \

Same here, and a couple more instances down below.

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