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From: Pelle Windestam <Pelle.Windestam@tagmaster.com>
To: "kernelnewbies@kernelnewbies.org" <kernelnewbies@kernelnewbies.org>
Subject: Accessing rpmsg_device in sysfs attribute functions
Date: Tue, 24 Mar 2020 05:34:44 +0000
Message-ID: <117a9e9d420f444ea814a37596fe5693@tagmaster.com> (raw)

Hi,

I am trying to develop a simple driver for the rpmsg bus, in order to send various commands from user space in Linux to a secondary CPU (A Cortex M4). I'm trying to keep things as simple as possible, so my idea was to create a driver that just has a few attributes which can be set in /sys which would trigger commands to be sent to the M4 CPU. I have the communication between the CPU:s up and running, but where I'm having trouble moving forward is how to access the "struct rpmsg_device *" that I need in order to communicate with the endpoint for the M4 CPU from the store/show function of the sysfs attributes. What my driver does is to register a rpmsg_driver in the init function:

register_rpmsg_driver(&pwm_rpmsg_driver);

the device_driver member of my rpmsg_driver struct has its groups member set to my driver attribute groups array:
static struct rpmsg_driver pwm_rpmsg_driver = {
	.probe = pwm_rpmsg_probe,
	.remove = pwm_rpmsg_remove,
	.callback = pwm_rpmsg_cb,
	.id_table = pwm_rpmsg_device_id_table,
	.drv = {
		.groups = driver_pwm_groups,
		.name = "pwm_rpmsg",
	},
};

My issue is that that I am not sure how to access the struct "rpmsg_device *" (i.e. from the probe() function) in the show/store functions for the sysfs attributes, which have a "struct device_driver *" argument:

static int pwm_rpmsg_probe(struct rpmsg_device *rpdev) /* rpmsg_device->ept is needed to send messages to the other CPU */

static ssize_t duty_cycle_store(struct device_driver *dev, const char *buf,
				      size_t count); /* Can I use the device_driver struct to somehow access the rpmsg_device? */

I am very much a novice when it comes to driver development, so I might be approaching this from a completely wrong direction. Any advice would be very much appreciated!

Thanks,
Pelle
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Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24  5:34 Pelle Windestam [this message]
2020-03-24  6:31 ` Greg KH
2020-03-24  9:49   ` Martin Kaiser
2020-03-24 10:23     ` Greg KH
2020-03-24 12:02   ` Pelle Windestam
2020-03-24 12:31     ` Greg KH
2020-03-24 13:05       ` Pelle Windestam
2020-03-24 13:15         ` Greg KH
2020-03-24 13:35           ` Pelle Windestam

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