lkml.org 
[lkml]   [2018]   [Dec]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v8 18/25] powerpc: Implement nvram sync ioctl
On Mon, 31 Dec 2018, Arnd Bergmann wrote:

> On Sun, Dec 30, 2018 at 8:25 AM Finn Thain <fthain@telegraphics.com.au> wrote:
> >
> > On Sat, 29 Dec 2018, Arnd Bergmann wrote:
> >
> > > > --- a/drivers/char/nvram.c
> > > > +++ b/drivers/char/nvram.c
> > > > @@ -48,6 +48,10 @@
> > > > #include <linux/mutex.h>
> > > > #include <linux/pagemap.h>
> > > >
> > > > +#ifdef CONFIG_PPC
> > > > +#include <asm/nvram.h>
> > > > +#include <asm/machdep.h>
> > > > +#endif
> > > >
> > > > static DEFINE_MUTEX(nvram_mutex);
> > > > static DEFINE_SPINLOCK(nvram_state_lock);
> > > > @@ -331,6 +335,37 @@ static long nvram_misc_ioctl(struct file *file, unsigned int cmd,
> > > > long ret = -ENOTTY;
> > > >
> > > > switch (cmd) {
> > > > +#ifdef CONFIG_PPC
> > > > + case OBSOLETE_PMAC_NVRAM_GET_OFFSET:
> > > > + pr_warn("nvram: Using obsolete PMAC_NVRAM_GET_OFFSET ioctl\n");
> > > > + /* fall through */
> > > > + case IOC_NVRAM_GET_OFFSET:
> > > > + ret = -EINVAL;
> > > > +#ifdef CONFIG_PPC_PMAC
> > >
> > > I think it would make be nicer here to keep the ppc bits in arch/ppc,
> > > and instead add a .ioctl() callback to nvram_ops.
> > >
> >
> > The problem with having an nvram_ops.ioctl() method is the code in the
> > !PPC branch. That code would get duplicated because it's needed by
> > both X86 and M68K, to implement the checksum ioctls.
>
> I was thinking you'd just have a common ioctl function that falls back
> to the .ioctl callback for any unhandled commands like
>
> switch (cmd) {
> case NVRAM_INIT:
> ...
> break;
> case ...:
> break;
> default:
> if (ops->ioctl)
> return ops->ioctl(...);
> return -EINVAL;
> }
>
> Would that work?
>

There are no ioctls common to all architectures. So your example becomes,

static long nvram_misc_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
if (ops->ioctl)
return ops->ioctl(file, cmd, arg);
return -ENOTTY;
}

And then my objection is the same: m68k and x86 now have to duplicate
their common ops->ioctl() implementation.

Here's a compromise that avoids some code duplication.

switch (cmd) {
#if defined(CONFIG_X86) || defined(CONFIG_M68K)
case NVRAM_INIT:
...
break;
case NVRAM_SETCKS:
...
break;
#endif
default:
if (ops->ioctl)
return ops->ioctl(...);
return -EINVAL;
}

But PPC64 and PPC32 also need to share their ops->ioctl() implementation.
It's not clear to me where that code would go.

Personally, I prefer the present patch series, or something similar, with
it's symmetry between nvram.c and nvram.h:

static long nvram_misc_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
long ret = -ENOTTY;

switch (cmd) {
#if defined(CONFIG_PPC)
case OBSOLETE_PMAC_NVRAM_GET_OFFSET:
...
case IOC_NVRAM_GET_OFFSET:
...
break;
case IOC_NVRAM_SYNC:
...
break;
#elif defined(CONFIG_X86) || defined(CONFIG_M68K)
case NVRAM_INIT:
...
break;
case NVRAM_SETCKS:
...
break;
#endif
}
return ret;
}

... versus the struct definition in nvram.h,

struct nvram_ops {
ssize_t (*read)(char *, size_t, loff_t *);
ssize_t (*write)(char *, size_t, loff_t *);
unsigned char (*read_byte)(int);
void (*write_byte)(unsigned char, int);
ssize_t (*get_size)(void);
#if defined(CONFIG_PPC)
long (*sync)(void);
int (*get_partition)(int);
#elif defined(CONFIG_X86) || defined(CONFIG_M68K)
long (*set_checksum)(void);
long (*initialize)(void);
#endif
};

Which of these alternatives do you prefer? Is there a better way?

--


> Arnd
>

\
 
 \ /
  Last update: 2019-01-01 02:07    [W:0.090 / U:0.788 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site