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Date: Thu, 26 Mar 2015 23:35:01 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, mathieu.poirier@...aro.org,
pebolle@...cali.nl, peter.lachner@...el.com,
norbert.schulz@...el.com, keven.boell@...el.com,
yann.fouassier@...el.com, laurent.fert@...el.com,
linux-api@...r.kernel.org, Pratik Patel <pratikp@...eaurora.org>
Subject: Re: [PATCH v2 01/11] stm class: Introduce an abstraction for System
Trace Module devices
On Sun, Mar 22, 2015 at 10:32:51PM +0200, Alexander Shishkin wrote:
> +static struct attribute *stm_attrs[] = {
> + &dev_attr_masters.attr,
> + &dev_attr_channels.attr,
> + NULL,
> +};
> +
> +static const struct attribute_group stm_group = {
> + .attrs = stm_attrs,
> +};
> +
> +static const struct attribute_group *stm_groups[] = {
> + &stm_group,
> + NULL,
> +};
> +
ATTRIBUTE_GROUP(stm)?
> +static struct class stm_class = {
> + .name = "stm",
> + .dev_groups = stm_groups,
> +};
> +
> +static int stm_dev_match(struct device *dev, const void *data)
> +{
> + const char *name = data;
> +
> + return sysfs_streq(name, dev_name(dev));
> +}
> +
> +/**
> + * stm_find_device() - find stm device by name
> + * @buf: character buffer containing the name
> + * @len: length of the name in @buf
> + *
> + * This is called from attributes' store methods, so it will
> + * also trim the trailing newline if necessary.
Why is this needed and the device isn't the one that was just passed to
you in the attribute store method?
> +static int stm_char_open(struct inode *inode, struct file *file)
> +{
> + struct stm_file *stmf;
> + struct device *dev;
> + unsigned int major = imajor(inode);
> + int err = -ENODEV;
> +
> + dev = class_find_device(&stm_class, NULL, &major, major_match);
> + if (!dev)
> + return -ENODEV;
Where are you documenting your character devices, the major/minor usage,
and the ioctls? Is that in some other patch?
> +static long
> +stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> + struct stm_file *stmf = file->private_data;
> + struct stm_data *stm_data = stmf->stm->data;
> + int err = -ENOTTY;
> +
> + switch (cmd) {
> + case STP_POLICY_ID_SET:
> + err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
Cast to the proper structure/type instead of void * please.
> + if (err)
> + return err;
> +
> + return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
Same here.
> +
> + case STP_POLICY_ID_GET:
> + return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
Same here.
> + default:
> + if (stm_data->ioctl)
> + err = stm_data->ioctl(stm_data, cmd, arg);
oh that's fun, two levels of ioctls, ugh, that makes auditing the code
hard...
> --- /dev/null
> +++ b/drivers/hwtracing/stm/stm.h
> @@ -0,0 +1,79 @@
> +/*
> + * System Trace Module (STM) infrastructure
> + * Copyright (c) 2014, Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope 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.
> + *
> + * STM class implements generic infrastructure for System Trace Module devices
> + * as defined in MIPI STPv2 specification.
> + */
> +
> +#ifndef _CLASS_STM_H_
> +#define _CLASS_STM_H_
"_CLASS_" ?
> +
> +struct stp_policy;
> +struct stp_policy_node;
> +
> +struct stp_policy_node *
> +stp_policy_node_lookup(struct stp_policy *policy, char *s);
> +void stp_policy_unbind(struct stp_policy *policy);
> +
> +void stp_policy_node_get_ranges(struct stp_policy_node *policy_node,
> + unsigned int *mstart, unsigned int *mend,
> + unsigned int *cstart, unsigned int *cend);
> +int stp_configfs_init(void);
> +void stp_configfs_exit(void);
> +
> +struct stp_master {
> + unsigned int nr_free;
> + unsigned long chan_map[0];
> +};
> +
> +struct stm_device {
> + struct device *dev;
> + struct module *owner;
> + struct stp_policy *policy;
> + struct mutex policy_mutex;
> + int major;
> + unsigned int sw_nmasters;
> + struct stm_data *data;
> + spinlock_t link_lock;
> + struct list_head link_list;
> + /* master allocation */
> + spinlock_t mc_lock;
> + struct stp_master *masters[0];
> +};
This is a "device" so please embed struct device into the device, don't
have it as a pointer.
And modules can not "own" data, they "own" code, so why does the device
have a module pointer?
Every device gets a new major number? Is that really needed?
> +struct stm_output {
> + unsigned int master;
> + unsigned int channel;
> + unsigned int nr_chans;
> +};
> +
> +struct stm_file {
> + struct stm_device *stm;
> + struct stp_policy_node *policy_node;
> + struct stm_output output;
> +};
> +
> +struct device *stm_find_device(const char *name, size_t len);
> +
> +struct stm_source_device {
> + struct device *dev;
Same device question here, this needs to be embedded, not a pointer, to
properly control the lifecycle of this structure.
> +/**
> + * struct stp_policy_id - identification for the STP policy
> + * @size: size of the structure including real id[] length
> + * @master: assigned master
> + * @channel: first assigned channel
> + * @width: number of requested channels
> + * @id: identification string
> + *
> + * User must calculate the total size of the structure and put it into
> + * @size field, fill out the @id and desired @width. In return, kernel
> + * fills out @master, @channel and @width.
> + */
> +struct stp_policy_id {
> + __u32 size;
> + __u16 master;
> + __u16 channel;
> + __u16 width;
> + /* padding */
> + __u16 __reserved_0;
> + __u32 __reserved_1;
> + char id[0];
> +};
> +
> +#define STP_POLICY_ID_SET _IOWR('%', 0, struct stp_policy_id)
> +#define STP_POLICY_ID_GET _IOR('%', 1, struct stp_policy_id)
Where did you get those ioctl numbers from?
And why need an ioctl at all?
thanks,
greg k-h
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