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Subject: Re: [PATCH V4 XRT Alveo 06/20] fpga: xrt: char dev node helper
 functions
To:     Lizhi Hou <lizhi.hou@xilinx.com>, linux-kernel@vger.kernel.org
Cc:     linux-fpga@vger.kernel.org, maxz@xilinx.com,
        sonal.santan@xilinx.com, yliu@xilinx.com, michal.simek@xilinx.com,
        stefanos@xilinx.com, devicetree@vger.kernel.org, mdf@kernel.org,
        robh@kernel.org, Max Zhen <max.zhen@xilinx.com>
References: <20210324052947.27889-1-lizhi.hou@xilinx.com>
 <20210324052947.27889-7-lizhi.hou@xilinx.com>
From:   Tom Rix <trix@redhat.com>
Message-ID: <755d73b9-1e23-c2e9-1502-15df14b9ed35@redhat.com>
Date:   Tue, 30 Mar 2021 06:45:11 -0700
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It is unclear from the changelog if this new patch was split from an existing patch or new content.

the file ops seem to come from mgmnt/main.c, which call what could be file ops here.  why is this complicated redirection needed ?

On 3/23/21 10:29 PM, Lizhi Hou wrote:
> Helper functions for char device node creation / removal for platform
> drivers. This is part of platform driver infrastructure.
>
> Signed-off-by: Sonal Santan <sonal.santan@xilinx.com>
> Signed-off-by: Max Zhen <max.zhen@xilinx.com>
> Signed-off-by: Lizhi Hou <lizhi.hou@xilinx.com>
> ---
>  drivers/fpga/xrt/lib/cdev.c | 232 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 232 insertions(+)
>  create mode 100644 drivers/fpga/xrt/lib/cdev.c
>
> diff --git a/drivers/fpga/xrt/lib/cdev.c b/drivers/fpga/xrt/lib/cdev.c
> new file mode 100644
> index 000000000000..38efd24b6e10
> --- /dev/null
> +++ b/drivers/fpga/xrt/lib/cdev.c
> @@ -0,0 +1,232 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Xilinx Alveo FPGA device node helper functions.
> + *
> + * Copyright (C) 2020-2021 Xilinx, Inc.
> + *
> + * Authors:
> + *	Cheng Zhen <maxz@xilinx.com>
> + */
> +
> +#include "xleaf.h"
> +
> +extern struct class *xrt_class;
> +
> +#define XRT_CDEV_DIR		"xfpga"
maybe "xrt_fpga" or just "xrt"
> +#define INODE2PDATA(inode)	\
> +	container_of((inode)->i_cdev, struct xrt_subdev_platdata, xsp_cdev)
> +#define INODE2PDEV(inode)	\
> +	to_platform_device(kobj_to_dev((inode)->i_cdev->kobj.parent))
> +#define CDEV_NAME(sysdev)	(strchr((sysdev)->kobj.name, '!') + 1)
> +
> +/* Allow it to be accessed from cdev. */
> +static void xleaf_devnode_allowed(struct platform_device *pdev)
> +{
> +	struct xrt_subdev_platdata *pdata = DEV_PDATA(pdev);
> +
> +	/* Allow new opens. */
> +	mutex_lock(&pdata->xsp_devnode_lock);
> +	pdata->xsp_devnode_online = true;
> +	mutex_unlock(&pdata->xsp_devnode_lock);
> +}
> +
> +/* Turn off access from cdev and wait for all existing user to go away. */
> +static int xleaf_devnode_disallowed(struct platform_device *pdev)
> +{
> +	int ret = 0;
> +	struct xrt_subdev_platdata *pdata = DEV_PDATA(pdev);
> +
> +	mutex_lock(&pdata->xsp_devnode_lock);
> +
> +	/* Prevent new opens. */
> +	pdata->xsp_devnode_online = false;
> +	/* Wait for existing user to close. */
> +	while (!ret && pdata->xsp_devnode_ref) {
> +		int rc;
> +
> +		mutex_unlock(&pdata->xsp_devnode_lock);
> +		rc = wait_for_completion_killable(&pdata->xsp_devnode_comp);
> +		mutex_lock(&pdata->xsp_devnode_lock);
> +
> +		if (rc == -ERESTARTSYS) {
> +			/* Restore online state. */
> +			pdata->xsp_devnode_online = true;
> +			xrt_err(pdev, "%s is in use, ref=%d",
> +				CDEV_NAME(pdata->xsp_sysdev),
> +				pdata->xsp_devnode_ref);
> +			ret = -EBUSY;
> +		}
> +	}
> +
> +	mutex_unlock(&pdata->xsp_devnode_lock);
> +
> +	return ret;
> +}
> +
> +static struct platform_device *
> +__xleaf_devnode_open(struct inode *inode, bool excl)
> +{
> +	struct xrt_subdev_platdata *pdata = INODE2PDATA(inode);
> +	struct platform_device *pdev = INODE2PDEV(inode);
> +	bool opened = false;
> +
> +	mutex_lock(&pdata->xsp_devnode_lock);
> +
> +	if (pdata->xsp_devnode_online) {
> +		if (excl && pdata->xsp_devnode_ref) {
> +			xrt_err(pdev, "%s has already been opened exclusively",
> +				CDEV_NAME(pdata->xsp_sysdev));
> +		} else if (!excl && pdata->xsp_devnode_excl) {
> +			xrt_err(pdev, "%s has been opened exclusively",
> +				CDEV_NAME(pdata->xsp_sysdev));
> +		} else {
> +			pdata->xsp_devnode_ref++;
> +			pdata->xsp_devnode_excl = excl;
> +			opened = true;
> +			xrt_info(pdev, "opened %s, ref=%d",
> +				 CDEV_NAME(pdata->xsp_sysdev),
> +				 pdata->xsp_devnode_ref);
> +		}
> +	} else {
> +		xrt_err(pdev, "%s is offline", CDEV_NAME(pdata->xsp_sysdev));
> +	}
> +
> +	mutex_unlock(&pdata->xsp_devnode_lock);
> +
> +	pdev = opened ? pdev : NULL;
> +	return pdev;
> +}
> +
> +struct platform_device *
> +xleaf_devnode_open_excl(struct inode *inode)
> +{
> +	return __xleaf_devnode_open(inode, true);
> +}
This function is unused, remove.
> +
> +struct platform_device *
> +xleaf_devnode_open(struct inode *inode)
> +{
> +	return __xleaf_devnode_open(inode, false);
> +}
> +EXPORT_SYMBOL_GPL(xleaf_devnode_open);
does this really need to be exported ?
> +
> +void xleaf_devnode_close(struct inode *inode)
> +{
> +	struct xrt_subdev_platdata *pdata = INODE2PDATA(inode);
> +	struct platform_device *pdev = INODE2PDEV(inode);
> +	bool notify = false;
> +
> +	mutex_lock(&pdata->xsp_devnode_lock);
> +
> +	WARN_ON(pdata->xsp_devnode_ref == 0);
> +	pdata->xsp_devnode_ref--;
> +	if (pdata->xsp_devnode_ref == 0) {
> +		pdata->xsp_devnode_excl = false;
> +		notify = true;
> +	}
> +	if (notify) {
> +		xrt_info(pdev, "closed %s, ref=%d",
> +			 CDEV_NAME(pdata->xsp_sysdev), pdata->xsp_devnode_ref);
xsp_devnode_ref will always be 0, so no need to report it.
> +	} else {
> +		xrt_info(pdev, "closed %s, notifying waiter",
> +			 CDEV_NAME(pdata->xsp_sysdev));
> +	}
> +
> +	mutex_unlock(&pdata->xsp_devnode_lock);
> +
> +	if (notify)
> +		complete(&pdata->xsp_devnode_comp);
> +}
> +EXPORT_SYMBOL_GPL(xleaf_devnode_close);
> +
> +static inline enum xrt_subdev_file_mode
> +devnode_mode(struct xrt_subdev_drvdata *drvdata)
> +{
> +	return drvdata->xsd_file_ops.xsf_mode;
> +}
> +
> +int xleaf_devnode_create(struct platform_device *pdev, const char *file_name,
> +			 const char *inst_name)
> +{
> +	struct xrt_subdev_drvdata *drvdata = DEV_DRVDATA(pdev);
> +	struct xrt_subdev_file_ops *fops = &drvdata->xsd_file_ops;
> +	struct xrt_subdev_platdata *pdata = DEV_PDATA(pdev);
> +	struct cdev *cdevp;
> +	struct device *sysdev;
> +	int ret = 0;
> +	char fname[256];
> +
> +	mutex_init(&pdata->xsp_devnode_lock);
> +	init_completion(&pdata->xsp_devnode_comp);
> +
> +	cdevp = &DEV_PDATA(pdev)->xsp_cdev;
> +	cdev_init(cdevp, &fops->xsf_ops);
> +	cdevp->owner = fops->xsf_ops.owner;
> +	cdevp->dev = MKDEV(MAJOR(fops->xsf_dev_t), pdev->id);
> +
> +	/*
> +	 * Set pdev as parent of cdev so that when pdev (and its platform
> +	 * data) will not be freed when cdev is not freed.
> +	 */
> +	cdev_set_parent(cdevp, &DEV(pdev)->kobj);
> +
> +	ret = cdev_add(cdevp, cdevp->dev, 1);
> +	if (ret) {
> +		xrt_err(pdev, "failed to add cdev: %d", ret);
> +		goto failed;
> +	}
> +	if (!file_name)
> +		file_name = pdev->name;
> +	if (!inst_name) {
> +		if (devnode_mode(drvdata) == XRT_SUBDEV_FILE_MULTI_INST) {
> +			snprintf(fname, sizeof(fname), "%s/%s/%s.%u",
> +				 XRT_CDEV_DIR, DEV_PDATA(pdev)->xsp_root_name,
> +				 file_name, pdev->id);
> +		} else {
> +			snprintf(fname, sizeof(fname), "%s/%s/%s",
> +				 XRT_CDEV_DIR, DEV_PDATA(pdev)->xsp_root_name,
> +				 file_name);
> +		}
> +	} else {
> +		snprintf(fname, sizeof(fname), "%s/%s/%s.%s", XRT_CDEV_DIR,
> +			 DEV_PDATA(pdev)->xsp_root_name, file_name, inst_name);
> +	}
> +	sysdev = device_create(xrt_class, NULL, cdevp->dev, NULL, "%s", fname);
> +	if (IS_ERR(sysdev)) {
> +		ret = PTR_ERR(sysdev);
> +		xrt_err(pdev, "failed to create device node: %d", ret);
> +		goto failed_cdev_add;
> +	}
> +	pdata->xsp_sysdev = sysdev;
> +
> +	xleaf_devnode_allowed(pdev);
> +
> +	xrt_info(pdev, "created (%d, %d): /dev/%s",
> +		 MAJOR(cdevp->dev), pdev->id, fname);
> +	return 0;
> +
> +failed_cdev_add:
> +	cdev_del(cdevp);
> +failed:
> +	cdevp->owner = NULL;
> +	return ret;
> +}
> +
> +int xleaf_devnode_destroy(struct platform_device *pdev)
> +{
> +	struct xrt_subdev_platdata *pdata = DEV_PDATA(pdev);
> +	struct cdev *cdevp = &pdata->xsp_cdev;
> +	dev_t dev = cdevp->dev;
> +	int rc;
> +
> +	rc = xleaf_devnode_disallowed(pdev);
> +	if (rc)
> +		return rc;

Failure of one leaf to be destroyed is not handled well.

could a able to destroy check be done over the whole group ?

Tom

> +
> +	xrt_info(pdev, "removed (%d, %d): /dev/%s/%s", MAJOR(dev), MINOR(dev),
> +		 XRT_CDEV_DIR, CDEV_NAME(pdata->xsp_sysdev));
> +	device_destroy(xrt_class, cdevp->dev);
> +	pdata->xsp_sysdev = NULL;
> +	cdev_del(cdevp);
> +	return 0;
> +}