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Message-ID: <20100805093236.GI26615@gundam.enneenne.com>
Date: Thu, 5 Aug 2010 11:32:36 +0200
From: Rodolfo Giometti <giometti@...eenne.com>
To: Alexander Gordeev <lasaine@....cs.msu.su>
Cc: linux-kernel@...r.kernel.org,
"Nikita V. Youshchenko" <yoush@...msu.su>,
linuxpps@...enneenne.com, john stultz <johnstul@...ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Tejun Heo <tj@...nel.org>, Joonwoo Park <joonwpark81@...il.com>
Subject: Re: [PATCHv3 05/16] pps: access pps device by direct pointer
On Thu, Aug 05, 2010 at 01:06:42AM +0400, Alexander Gordeev wrote:
> Using device index as a pointer needs some unnecessary work to be done
> every time the pointer is needed (in irq handler for example).
> Using a direct pointer is much more easy (and safe as well).
>
> Signed-off-by: Alexander Gordeev <lasaine@....cs.msu.su>
> ---
> drivers/pps/clients/pps-ktimer.c | 30 ++++-----
> drivers/pps/clients/pps-ldisc.c | 33 +++++-----
> drivers/pps/kapi.c | 124 ++++++++-----------------------------
> drivers/pps/pps.c | 22 ++-----
> include/linux/pps_kernel.h | 21 +++----
> 5 files changed, 70 insertions(+), 160 deletions(-)
>
> diff --git a/drivers/pps/clients/pps-ktimer.c b/drivers/pps/clients/pps-ktimer.c
> index e1bdd8b..64cba1d 100644
> --- a/drivers/pps/clients/pps-ktimer.c
> +++ b/drivers/pps/clients/pps-ktimer.c
> @@ -31,7 +31,7 @@
> * Global variables
> */
>
> -static int source;
> +static struct pps_device *pps;;
> static struct timer_list ktimer;
>
> /*
> @@ -47,7 +47,7 @@ static void pps_ktimer_event(unsigned long ptr)
>
> pr_info("PPS event at %lu\n", jiffies);
>
> - pps_event(source, &ts, PPS_CAPTUREASSERT, NULL);
> + pps_event(pps, &ts, PPS_CAPTUREASSERT, NULL);
>
> mod_timer(&ktimer, jiffies + HZ);
> }
> @@ -56,12 +56,11 @@ static void pps_ktimer_event(unsigned long ptr)
> * The echo function
> */
>
> -static void pps_ktimer_echo(int source, int event, void *data)
> +static void pps_ktimer_echo(struct pps_device *pps, int event, void *data)
> {
> - pr_info("echo %s %s for source %d\n",
> + dev_info(pps->dev, "echo %s %s\n",
> event & PPS_CAPTUREASSERT ? "assert" : "",
> - event & PPS_CAPTURECLEAR ? "clear" : "",
> - source);
> + event & PPS_CAPTURECLEAR ? "clear" : "");
> }
>
> /*
> @@ -84,30 +83,27 @@ static struct pps_source_info pps_ktimer_info = {
>
> static void __exit pps_ktimer_exit(void)
> {
> - del_timer_sync(&ktimer);
> - pps_unregister_source(source);
> + dev_info(pps->dev, "ktimer PPS source unregistered\n");
>
> - pr_info("ktimer PPS source unregistered\n");
> + del_timer_sync(&ktimer);
> + pps_unregister_source(pps);
> }
>
> static int __init pps_ktimer_init(void)
> {
> - int ret;
> -
> - ret = pps_register_source(&pps_ktimer_info,
> + pps = pps_register_source(&pps_ktimer_info,
> PPS_CAPTUREASSERT | PPS_OFFSETASSERT);
> - if (ret < 0) {
> + if (pps == NULL) {
> printk(KERN_ERR "cannot register ktimer source\n");
> - return ret;
> + return -ENOMEM;
> }
> - source = ret;
>
> setup_timer(&ktimer, pps_ktimer_event, 0);
> mod_timer(&ktimer, jiffies + HZ);
>
> - pr_info("ktimer PPS source registered at %d\n", source);
> + dev_info(pps->dev, "ktimer PPS source registered\n");
>
> - return 0;
> + return 0;
> }
>
> module_init(pps_ktimer_init);
> diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c
> index 20fc9f7..d7e1a27 100644
> --- a/drivers/pps/clients/pps-ldisc.c
> +++ b/drivers/pps/clients/pps-ldisc.c
> @@ -29,7 +29,7 @@
> static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
> struct pps_event_time *ts)
> {
> - int id = (long)tty->disc_data;
> + struct pps_device *pps = (struct pps_device *)tty->disc_data;
> struct pps_event_time __ts;
>
> /* First of all we get the time stamp... */
> @@ -40,11 +40,11 @@ static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
> ts = &__ts;
>
> /* Now do the PPS event report */
> - pps_event(id, ts, status ? PPS_CAPTUREASSERT : PPS_CAPTURECLEAR,
> + pps_event(pps, ts, status ? PPS_CAPTUREASSERT : PPS_CAPTURECLEAR,
> NULL);
>
> - pr_debug("PPS %s at %lu on source #%d\n",
> - status ? "assert" : "clear", jiffies, id);
> + dev_dbg(pps->dev, "PPS %s at %lu\n", status ? "assert" : "clear",
> + jiffies);
> }
>
> static int (*alias_n_tty_open)(struct tty_struct *tty);
> @@ -54,7 +54,7 @@ static int pps_tty_open(struct tty_struct *tty)
> struct pps_source_info info;
> struct tty_driver *drv = tty->driver;
> int index = tty->index + drv->name_base;
> - int ret;
> + struct pps_device *pps;
>
> info.owner = THIS_MODULE;
> info.dev = NULL;
> @@ -64,20 +64,19 @@ static int pps_tty_open(struct tty_struct *tty)
> PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
> PPS_CANWAIT | PPS_TSFMT_TSPEC;
>
> - ret = pps_register_source(&info, PPS_CAPTUREBOTH | \
> + pps = pps_register_source(&info, PPS_CAPTUREBOTH | \
> PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
> - if (ret < 0) {
> + if (pps == NULL) {
> pr_err("cannot register PPS source \"%s\"\n", info.path);
> - return ret;
> + return -ENOMEM;
> }
> - tty->disc_data = (void *)(long)ret;
> + tty->disc_data = pps;
>
> /* Should open N_TTY ldisc too */
> - ret = alias_n_tty_open(tty);
> - if (ret < 0)
> - pps_unregister_source((long)tty->disc_data);
> + if (alias_n_tty_open(tty) < 0)
> + pps_unregister_source(pps);
>
> - pr_info("PPS source #%d \"%s\" added\n", ret, info.path);
> + dev_info(pps->dev, "source \"%s\" added\n", info.path);
>
> return 0;
> }
> @@ -86,12 +85,12 @@ static void (*alias_n_tty_close)(struct tty_struct *tty);
>
> static void pps_tty_close(struct tty_struct *tty)
> {
> - int id = (long)tty->disc_data;
> + struct pps_device *pps = (struct pps_device *)tty->disc_data;
>
> - pps_unregister_source(id);
> - alias_n_tty_close(tty);
> + dev_info(pps->dev, "removed\n");
>
> - pr_info("PPS source #%d removed\n", id);
> + pps_unregister_source(pps);
> + alias_n_tty_close(tty);
> }
>
> static struct tty_ldisc_ops pps_ldisc_ops;
> diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
> index b431d83..568223b 100644
> --- a/drivers/pps/kapi.c
> +++ b/drivers/pps/kapi.c
> @@ -32,11 +32,11 @@
> #include <linux/slab.h>
>
> /*
> - * Global variables
> + * Local variables
> */
>
> -DEFINE_SPINLOCK(pps_idr_lock);
> -DEFINE_IDR(pps_idr);
> +static DEFINE_SPINLOCK(pps_idr_lock);
> +static DEFINE_IDR(pps_idr);
>
> /*
> * Local functions
> @@ -60,60 +60,6 @@ static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
> * Exported functions
> */
>
> -/* pps_get_source - find a PPS source
> - * @source: the PPS source ID.
> - *
> - * This function is used to find an already registered PPS source into the
> - * system.
> - *
> - * The function returns NULL if found nothing, otherwise it returns a pointer
> - * to the PPS source data struct (the refcounter is incremented by 1).
> - */
> -
> -struct pps_device *pps_get_source(int source)
> -{
> - struct pps_device *pps;
> - unsigned long flags;
> -
> - spin_lock_irqsave(&pps_idr_lock, flags);
> -
> - pps = idr_find(&pps_idr, source);
> - if (pps != NULL)
> - atomic_inc(&pps->usage);
> -
> - spin_unlock_irqrestore(&pps_idr_lock, flags);
> -
> - return pps;
> -}
> -
> -/* pps_put_source - free the PPS source data
> - * @pps: a pointer to the PPS source.
> - *
> - * This function is used to free a PPS data struct if its refcount is 0.
> - */
> -
> -void pps_put_source(struct pps_device *pps)
> -{
> - unsigned long flags;
> -
> - spin_lock_irqsave(&pps_idr_lock, flags);
> - BUG_ON(atomic_read(&pps->usage) == 0);
> -
> - if (!atomic_dec_and_test(&pps->usage)) {
> - pps = NULL;
> - goto exit;
> - }
> -
> - /* No more reference to the PPS source. We can safely remove the
> - * PPS data struct.
> - */
> - idr_remove(&pps_idr, pps->id);
> -
> -exit:
> - spin_unlock_irqrestore(&pps_idr_lock, flags);
> - kfree(pps);
> -}
If you remove these functions you can't be sure anymore that nobodies
may call pps_event() over a non existent device...
> /* pps_register_source - add a PPS source in the system
> * @info: the PPS info struct
> * @default_params: the default PPS parameters of the new source
> @@ -122,10 +68,11 @@ exit:
> * source is described by info's fields and it will have, as default PPS
> * parameters, the ones specified into default_params.
> *
> - * The function returns, in case of success, the PPS source ID.
> + * The function returns, in case of success, the PPS device. Otherwise NULL.
> */
>
> -int pps_register_source(struct pps_source_info *info, int default_params)
> +struct pps_device *pps_register_source(struct pps_source_info *info,
> + int default_params)
> {
> struct pps_device *pps;
> int id;
> @@ -168,7 +115,6 @@ int pps_register_source(struct pps_source_info *info, int default_params)
>
> init_waitqueue_head(&pps->queue);
> spin_lock_init(&pps->lock);
> - atomic_set(&pps->usage, 1);
>
> /* Get new ID for the new PPS source */
> if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {
> @@ -211,7 +157,7 @@ int pps_register_source(struct pps_source_info *info, int default_params)
>
> pr_info("new PPS source %s at ID %d\n", info->name, id);
>
> - return id;
> + return pps;
>
> free_idr:
> spin_lock_irq(&pps_idr_lock);
> @@ -224,38 +170,31 @@ kfree_pps:
> pps_register_source_exit:
> printk(KERN_ERR "pps: %s: unable to register source\n", info->name);
>
> - return err;
> + return NULL;
> }
> EXPORT_SYMBOL(pps_register_source);
>
> /* pps_unregister_source - remove a PPS source from the system
> - * @source: the PPS source ID
> + * @pps: the PPS source
> *
> * This function is used to remove a previously registered PPS source from
> * the system.
> */
>
> -void pps_unregister_source(int source)
> +void pps_unregister_source(struct pps_device *pps)
> {
> - struct pps_device *pps;
> + unsigned int id = pps->id;
>
> + pps_unregister_cdev(pps);
> +
> spin_lock_irq(&pps_idr_lock);
> - pps = idr_find(&pps_idr, source);
> -
> - if (!pps) {
> - BUG();
> - spin_unlock_irq(&pps_idr_lock);
> - return;
> - }
> + idr_remove(&pps_idr, pps->id);
> spin_unlock_irq(&pps_idr_lock);
> -
> - pps_unregister_cdev(pps);
> - pps_put_source(pps);
> }
> EXPORT_SYMBOL(pps_unregister_source);
>
> /* pps_event - register a PPS event into the system
> - * @source: the PPS source ID
> + * @pps: the PPS device
> * @ts: the event timestamp
> * @event: the event type
> * @data: userdef pointer
> @@ -263,30 +202,24 @@ EXPORT_SYMBOL(pps_unregister_source);
> * This function is used by each PPS client in order to register a new
> * PPS event into the system (it's usually called inside an IRQ handler).
> *
> - * If an echo function is associated with the PPS source it will be called
> + * If an echo function is associated with the PPS device it will be called
> * as:
> - * pps->info.echo(source, event, data);
> + * pps->info.echo(pps, event, data);
> */
> -
> -void pps_event(int source, struct pps_event_time *ts, int event, void *data)
> +void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
> + void *data)
> {
> - struct pps_device *pps;
> unsigned long flags;
> int captured = 0;
> struct pps_ktime ts_real;
>
> if ((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0) {
> - printk(KERN_ERR "pps: unknown event (%x) for source %d\n",
> - event, source);
> + dev_err(pps->dev, "unknown event (%x)\n", event);
> return;
> }
>
> - pps = pps_get_source(source);
> - if (!pps)
> - return;
> -
> - pr_debug("PPS event on source %d at %ld.%09ld\n",
> - pps->id, ts->ts_real.tv_sec, ts->ts_real.tv_nsec);
> + dev_dbg(pps->dev, "PPS event at %ld.%09ld\n",
> + ts->ts_real.tv_sec, ts->ts_real.tv_nsec);
By dropping pps_get_source you may be here by a call from (i.e.) a
serial port driver whose doesn't know if your PPS source is gone or
not...
I don't understand how your modifications may resolve this problem.
> timespec_to_pps_ktime(&ts_real, ts->ts_real);
>
> @@ -294,7 +227,7 @@ void pps_event(int source, struct pps_event_time *ts, int event, void *data)
>
> /* Must call the echo function? */
> if ((pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)))
> - pps->info.echo(source, event, data);
> + pps->info.echo(pps, event, data);
>
> /* Check the event */
> pps->current_mode = pps->params.mode;
> @@ -308,8 +241,8 @@ void pps_event(int source, struct pps_event_time *ts, int event, void *data)
> /* Save the time stamp */
> pps->assert_tu = ts_real;
> pps->assert_sequence++;
> - pr_debug("capture assert seq #%u for source %d\n",
> - pps->assert_sequence, source);
> + dev_dbg(pps->dev, "capture assert seq #%u\n",
> + pps->assert_sequence);
>
> captured = ~0;
> }
> @@ -323,8 +256,8 @@ void pps_event(int source, struct pps_event_time *ts, int event, void *data)
> /* Save the time stamp */
> pps->clear_tu = ts_real;
> pps->clear_sequence++;
> - pr_debug("capture clear seq #%u for source %d\n",
> - pps->clear_sequence, source);
> + dev_dbg(pps->dev, "capture clear seq #%u\n",
> + pps->clear_sequence);
>
> captured = ~0;
> }
> @@ -338,8 +271,5 @@ void pps_event(int source, struct pps_event_time *ts, int event, void *data)
> }
>
> spin_unlock_irqrestore(&pps->lock, flags);
> -
> - /* Now we can release the PPS source for (possible) deregistration */
> - pps_put_source(pps);
> }
> EXPORT_SYMBOL(pps_event);
> diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
> index cb24147..89f478b 100644
> --- a/drivers/pps/pps.c
> +++ b/drivers/pps/pps.c
> @@ -204,12 +204,6 @@ static int pps_cdev_open(struct inode *inode, struct file *file)
> {
> struct pps_device *pps = container_of(inode->i_cdev,
> struct pps_device, cdev);
> - int found;
> -
> - found = pps_get_source(pps->id) != 0;
> - if (!found)
> - return -ENODEV;
> -
> file->private_data = pps;
>
> return 0;
> @@ -217,11 +211,6 @@ static int pps_cdev_open(struct inode *inode, struct file *file)
>
> static int pps_cdev_release(struct inode *inode, struct file *file)
> {
> - struct pps_device *pps = file->private_data;
> -
> - /* Free the PPS source and wake up (possible) deregistration */
> - pps_put_source(pps);
> -
> return 0;
> }
>
> @@ -242,22 +231,23 @@ static const struct file_operations pps_cdev_fops = {
> int pps_register_cdev(struct pps_device *pps)
> {
> int err;
> + dev_t devt;
> +
> + devt = MKDEV(MAJOR(pps_devt), pps->id);
>
> - pps->devno = MKDEV(MAJOR(pps_devt), pps->id);
> cdev_init(&pps->cdev, &pps_cdev_fops);
> pps->cdev.owner = pps->info.owner;
>
> - err = cdev_add(&pps->cdev, pps->devno, 1);
> + err = cdev_add(&pps->cdev, devt, 1);
> if (err) {
> printk(KERN_ERR "pps: %s: failed to add char device %d:%d\n",
> pps->info.name, MAJOR(pps_devt), pps->id);
> return err;
> }
> - pps->dev = device_create(pps_class, pps->info.dev, pps->devno, NULL,
> + pps->dev = device_create(pps_class, pps->info.dev, devt, pps,
> "pps%d", pps->id);
> if (IS_ERR(pps->dev))
> goto del_cdev;
> - dev_set_drvdata(pps->dev, pps);
>
> pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
> MAJOR(pps_devt), pps->id);
> @@ -272,7 +262,7 @@ del_cdev:
>
> void pps_unregister_cdev(struct pps_device *pps)
> {
> - device_destroy(pps_class, pps->devno);
> + device_destroy(pps_class, pps->dev->devt);
> cdev_del(&pps->cdev);
> }
>
> diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
> index 32aa676..1e0f249 100644
> --- a/include/linux/pps_kernel.h
> +++ b/include/linux/pps_kernel.h
> @@ -31,13 +31,16 @@
> * Global defines
> */
>
> +struct pps_device;
> +
> /* The specific PPS source info */
> struct pps_source_info {
> char name[PPS_MAX_NAME_LEN]; /* simbolic name */
> char path[PPS_MAX_NAME_LEN]; /* path of connected device */
> int mode; /* PPS's allowed mode */
>
> - void (*echo)(int source, int event, void *data); /* PPS echo function */
> + void (*echo)(struct pps_device *pps,
> + int event, void *data); /* PPS echo function */
>
> struct module *owner;
> struct device *dev;
> @@ -65,34 +68,26 @@ struct pps_device {
> unsigned int id; /* PPS source unique ID */
> struct cdev cdev;
> struct device *dev;
> - int devno;
> struct fasync_struct *async_queue; /* fasync method */
> spinlock_t lock;
> -
> - atomic_t usage; /* usage count */
> };
>
> /*
> * Global variables
> */
>
> -extern spinlock_t pps_idr_lock;
> -extern struct idr pps_idr;
> -
> extern struct device_attribute pps_attrs[];
>
> /*
> * Exported functions
> */
>
> -struct pps_device *pps_get_source(int source);
> -extern void pps_put_source(struct pps_device *pps);
> -extern int pps_register_source(struct pps_source_info *info,
> - int default_params);
> -extern void pps_unregister_source(int source);
> +extern struct pps_device *pps_register_source(
> + struct pps_source_info *info, int default_params);
> +extern void pps_unregister_source(struct pps_device *pps);
> extern int pps_register_cdev(struct pps_device *pps);
> extern void pps_unregister_cdev(struct pps_device *pps);
> -extern void pps_event(int source, struct pps_event_time *ts, int event,
> +extern void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event,
> void *data);
>
> static inline void timespec_to_pps_ktime(struct pps_ktime *kt,
> --
> 1.7.1
>
--
GNU/Linux Solutions e-mail: giometti@...eenne.com
Linux Device Driver giometti@...ux.it
Embedded Systems phone: +39 349 2432127
UNIX programming skype: rodolfo.giometti
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