ALSA: xen: Convert to generic PCM copy ops

This patch converts the xen frontend driver code to use the new
unified PCM copy callback. It's a straightforward conversion from
*_user() to *_iter() variants.

Note that copy_from/to_iter() returns the copied bytes, hence the
error condition is adjusted accordingly.

Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: xen-devel@lists.xenproject.org
Link: https://lore.kernel.org/r/20230815190136.8987-16-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: xen-front: refactor deprecated strncpy

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

A suitable replacement is `strscpy` [2] due to the fact that it
guarantees NUL-termination on its destination buffer argument which is
_not_ always the case for `strncpy`!

It should be noted that, in this case, the destination buffer has a
length strictly greater than the source string. Moreover, the source
string is NUL-terminated (and so is the destination) which means there
was no real bug happening here. Nonetheless, this patch would get us one
step closer to eliminating the `strncpy` API in the kernel, as its use
is too ambiguous. We need to favor less ambiguous replacements such as:
strscpy, strscpy_pad, strtomem and strtomem_pad (amongst others).

Technically, my patch yields subtly different behavior. The original
implementation with `strncpy` would fill the entire destination buffer
with null bytes [3] while `strscpy` will leave the junk, uninitialized
bytes trailing after the _mandatory_ NUL-termination. So, if somehow
`pcm->name` or `card->driver/shortname/longname` require this
NUL-padding behavior then `strscpy_pad` should be used. My
interpretation, though, is that the aforementioned fields are just fine
as NUL-terminated strings. Please correct my assumptions if needed and
I'll send in a v2.

[1]: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
[2]: manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
[3]: https://linux.die.net/man/3/strncpy

Link: https://github.com/KSPP/linux/issues/90
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230727-sound-xen-v1-1-89dd161351f1@google.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: xen: Drop superfluous ioctl PCM ops

PCM core deals the empty ioctl field now as default(*).
Let's kill the redundant lines.

(*) commit fc033cbf6fb7 ("ALSA: pcm: Allow NULL ioctl ops")

Link: https://lore.kernel.org/r/20191210061145.24641-24-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: xen-front: fix unintention integer overflow on left shifts

Shifting the integer value 1 is evaluated using 32-bit
arithmetic and then used in an expression that expects a 64-bit
value, so there is potentially an integer overflow. Fix this
by using the BIT_ULL macro to perform the shift.

[ Note: as of the time being, no actual integer overflow hits because
all values are less than 32bit, not including the extended 3-byte or
DSD formats. But this is the right fix for future usage, of
course. -- tiwai ]

Addresses-Coverity: ("Unintentional integer overflow")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: xen-front: Do not use stream buffer size before it is set

This fixes the regression introduced while moving to Xen shared
buffer implementation.

Fixes: 58f9d806d16a ("ALSA: xen-front: Use Xen common shared buffer implementation")
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: <stable@vger.kernel.org> # v5.0+
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: xen-front: Use Xen common shared buffer implementation

Use page directory based shared buffer implementation
now available as common code for Xen frontend drivers.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

ALSA: xen-front: Refine indentations and constify snd_pcm_ops

snd_pcm_ops are not supposed to change. So mark the
non-const structs as const. Also, refine indentation
to ncrease readability.

Signed-off-by: Nick Simonov <nicksimonovv@gmail.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: xen: Use standard pcm_format_to_bits() for ALSA format bits

The open codes with the bit shift in xen_snd_front_alsa.c give sparse
warnings as the PCM format type is with __bitwise.
There is already a standard macro to get the format bits, so let's use
it instead.

This fixes sparse warnings like:
sound/xen/xen_snd_front_alsa.c:191:47: warning: restricted snd_pcm_format_t degrades to integer

Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: xen-front: fix unsigned error check on return from to_sndif_format

The negative error return from the call to to_sndif_format is being
assigned to an unsigned 8 bit integer and hence the check for a negative
value is always going to be false. Fix this by using ret as the error
return and hence the negative error can be detected and assign
the u8 sndif_format to ret if there is no error.

Detected by CoverityScan, CID#1469385 ("Unsigned compared against 0")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Takashi Sakamoto <o-takashi@sakamoccchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

ALSA: xen-front: Implement ALSA virtual sound driver

Implement essential initialization of the sound driver:
- introduce required data structures
- handle driver registration
- handle sound card registration
- register sound driver on backend connection
- remove sound driver on backend disconnect

Initialize virtual sound card with streams according to the
Xen store configuration.

Implement ALSA driver operations including:
- manage frontend/backend shared buffers
- manage Xen bus event channel states

Implement requests from front to back for ALSA
PCM operations.
- report ALSA period elapsed event: handle XENSND_EVT_CUR_POS
notifications from the backend when stream position advances
during playback/capture. The event carries a value of how
many octets were played/captured at the time of the event.
- implement explicit stream parameter negotiation between
backend and frontend: handle XENSND_OP_HW_PARAM_QUERY request
to read/update configuration space for the parameter given:
request passes desired parameter interval and the response to
this request returns min/max interval for the parameter to be used.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>