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Message-ID: <2501afe78a6e5027a0d5f270d6ef8a897564e5dc.camel@ozlabs.org>
Date: Wed, 15 Dec 2021 17:06:13 +1100
From: Amitay Isaacs <amitay@...abs.org>
To: Andrew Jeffery <andrew@...id.au>, linux-kernel@...r.kernel.org,
linux-fsi@...ts.ozlabs.org, Jeremy Kerr <jk@...abs.org>,
Joel Stanley <joel@....id.au>,
Alistair Popple <alistair@...ple.id.au>,
Eddie James <eajames@...ux.ibm.com>
Subject: Re: [PATCH 2/2] fsi: sbefifo: implement FSI_SBEFIFO_READ_TIMEOUT
ioctl
Hi Andrew,
On Wed, 2021-12-15 at 16:13 +1030, Andrew Jeffery wrote:
> Hi Amitay,
>
> On Wed, 15 Dec 2021, at 11:28, Amitay Isaacs wrote:
> > FSI_SBEFIFO_READ_TIMEOUT ioctl sets the read timeout (in seconds)
> > for
> > the response to *the next* chip-op sent to sbe. The timeout value
> > is
> > reset to default after the chip-op.
>
> For the user? Why reset it automatically? To avoid unexpected
> surprises in existing code?
Ideally I would prefer the timeout as an argument for the read() call,
so it's specific to that read call and nothing else. Of course, this
simplifies the user-space code that needs to issue only a single ioctl
before the "long" chip-ops.
I am fine with using the ioctl to just set the timeout value also.
>
> > The timeout affects only the read()
> > operation on sbefifo device fd.
> >
> > Signed-off-by: Amitay Isaacs <amitay@...abs.org>
> > ---
> > drivers/fsi/fsi-sbefifo.c | 42
> > +++++++++++++++++++++++++++++++++++++++
> > include/uapi/linux/fsi.h | 6 ++++++
> > 2 files changed, 48 insertions(+)
> >
> > diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
> > index 9188161f440c..b2654b143b85 100644
> > --- a/drivers/fsi/fsi-sbefifo.c
> > +++ b/drivers/fsi/fsi-sbefifo.c
> > @@ -32,6 +32,8 @@
> > #include <linux/vmalloc.h>
> > #include <linux/mm.h>
> >
> > +#include <uapi/linux/fsi.h>
> > +
> > /*
> > * The SBEFIFO is a pipe-like FSI device for communicating with
> > * the self boot engine on POWER processors.
> > @@ -134,6 +136,7 @@ struct sbefifo_user {
> > void *cmd_page;
> > void *pending_cmd;
> > size_t pending_len;
> > + uint32_t read_timeout_ms;
> > };
> >
> > static DEFINE_MUTEX(sbefifo_ffdc_mutex);
> > @@ -796,6 +799,7 @@ static int sbefifo_user_open(struct inode
> > *inode,
> > struct file *file)
> > return -ENOMEM;
> > }
> > mutex_init(&user->file_lock);
> > + user->read_timeout_ms = SBEFIFO_TIMEOUT_START_RSP;
> >
> > return 0;
> > }
> > @@ -838,7 +842,11 @@ static ssize_t sbefifo_user_read(struct file
> > *file, char __user *buf,
> > rc = mutex_lock_interruptible(&sbefifo->lock);
> > if (rc)
> > goto bail;
> > + sbefifo->timeout_start_rsp_ms = user->read_timeout_ms;
> > rc = __sbefifo_submit(sbefifo, user->pending_cmd, cmd_len,
> > &resp_iter);
> > + /* Reset the read timeout after a single chip-op */
> > + sbefifo->timeout_start_rsp_ms = SBEFIFO_TIMEOUT_START_RSP;
> > + user->read_timeout_ms = SBEFIFO_TIMEOUT_START_RSP;
>
> I guess I was querying this one
>
> > mutex_unlock(&sbefifo->lock);
> > if (rc < 0)
> > goto bail;
> > @@ -847,6 +855,7 @@ static ssize_t sbefifo_user_read(struct file
> > *file,
> > char __user *buf,
> > rc = len - iov_iter_count(&resp_iter);
> > bail:
> > sbefifo_release_command(user);
> > + user->read_timeout_ms = 0;
> > mutex_unlock(&user->file_lock);
> > return rc;
> > }
> > @@ -928,12 +937,45 @@ static int sbefifo_user_release(struct inode
> > *inode, struct file *file)
> > return 0;
> > }
> >
> > +static int sbefifo_read_timeout(struct sbefifo_user *user, void
> > __user
> > **argp)
> > +{
> > + uint32_t timeout;
> > +
> > + if (get_user(timeout, (__u32 __user *)argp))
>
> Hmm
>
> > + return -EFAULT;
> > + if (timeout < 10 || timeout > 120)
> > + return -EINVAL;
> > +
> > + user->read_timeout_ms = timeout * 1000; /* user timeout is
> > in sec */
> > + return 0;
> > +}
> > +
> > +static long sbefifo_user_ioctl(struct file *file, unsigned int
> > cmd,
> > unsigned long arg)
> > +{
> > + struct sbefifo_user *user = file->private_data;
> > + void __user **argp = (void __user *)arg;
>
> Why are we doing strange things with the pointer types?
That's what the ioctl implementation for fsi does. (Monkey see, monkey
copy!) :-)
>
> Andrew
>
> > + int rc = -ENOTTY;
> > +
> > + if (!user)
> > + return -EINVAL;
> > +
> > + mutex_lock(&user->file_lock);
> > + switch (cmd) {
> > + case FSI_SBEFIFO_READ_TIMEOUT:
> > + rc = sbefifo_read_timeout(user, argp);
> > + break;
> > + }
> > + mutex_unlock(&user->file_lock);
> > + return rc;
> > +}
> > +
> > static const struct file_operations sbefifo_fops = {
> > .owner = THIS_MODULE,
> > .open = sbefifo_user_open,
> > .read = sbefifo_user_read,
> > .write = sbefifo_user_write,
> > .release = sbefifo_user_release,
> > + .unlocked_ioctl = sbefifo_user_ioctl,
> > };
> >
> > static void sbefifo_free(struct device *dev)
> > diff --git a/include/uapi/linux/fsi.h b/include/uapi/linux/fsi.h
> > index da577ecd90e7..3e00874ace22 100644
> > --- a/include/uapi/linux/fsi.h
> > +++ b/include/uapi/linux/fsi.h
> > @@ -55,4 +55,10 @@ struct scom_access {
> > #define FSI_SCOM_WRITE _IOWR('s', 0x02, struct scom_access)
> > #define FSI_SCOM_RESET _IOW('s', 0x03, __u32)
> >
> > +/*
> > + * /dev/sbefifo* ioctl interface
> > + */
> > +
> > +#define FSI_SBEFIFO_READ_TIMEOUT _IOW('s', 0x00, __u32)
> > +
> > #endif /* _UAPI_LINUX_FSI_H */
> > --
> > 2.33.1
Amitay.
--
There will always be rocks in the road ahead of you.
They will be stumbling blocks or stepping stones;
It all depends on how you use them
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