Add support for Linux I2C character device for I2C device passthrough
For example:
-chardev linux-i2c,address=0x46,path=/dev/i2c-N,id=i2c-chardev

Signed-off-by: Ernest Esene <eroken1@gmail.com>
---
 chardev/Makefile.objs  |   1 +
 chardev/char-i2c.c     | 142 +++++++++++++++++++++++++++++++++++++++++++++++++
 chardev/char.c         |   3 ++
 include/chardev/char.h |   1 +
 qapi/char.json         |  16 ++++++
 5 files changed, 163 insertions(+)
 create mode 100644 chardev/char-i2c.c

diff --git a/chardev/Makefile.objs b/chardev/Makefile.objs
index d68e1347f9..6c96b9a353 100644
--- a/chardev/Makefile.objs
+++ b/chardev/Makefile.objs
@@ -16,6 +16,7 @@ chardev-obj-y += char-stdio.o
 chardev-obj-y += char-udp.o
 chardev-obj-$(CONFIG_WIN32) += char-win.o
 chardev-obj-$(CONFIG_WIN32) += char-win-stdio.o
+chardev-obj-$(CONFIG_POSIX) +=char-i2c.o
 
 common-obj-y += msmouse.o wctablet.o testdev.o
 common-obj-$(CONFIG_BRLAPI) += baum.o
diff --git a/chardev/char-i2c.c b/chardev/char-i2c.c
new file mode 100644
index 0000000000..78cf973bd7
--- /dev/null
+++ b/chardev/char-i2c.c
@@ -0,0 +1,142 @@
+/*
+ * QEMU System Emulator
+ *
+ * Copyright (c) 2019 Ernest Esene <eroken1@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu/option.h"
+#include "qemu-common.h"
+#include "io/channel-file.h"
+
+#include "chardev/char-fd.h"
+#include "chardev/char.h"
+
+#include <sys/ioctl.h>
+#include <linux/i2c-dev.h>
+
+#define CHR_IOCTL_I2C_SET_ADDR 1
+
+#define CHR_I2C_ADDR_10BIT_MAX 1023
+#define CHR_I2C_ADDR_7BIT_MAX 127
+
+void qemu_set_block(int fd);
+
+static int i2c_ioctl(Chardev *chr, int cmd, void *arg)
+{
+    FDChardev *fd_chr = FD_CHARDEV(chr);
+    QIOChannelFile *floc = QIO_CHANNEL_FILE(fd_chr->ioc_in);
+    int fd = floc->fd;
+    int addr;
+
+    switch (cmd) {
+        case CHR_IOCTL_I2C_SET_ADDR:
+            addr = (int) (long) arg;
+
+            if (addr > CHR_I2C_ADDR_7BIT_MAX) {
+                /*TODO: check if adapter support 10-bit addr
+                I2C_FUNC_10BIT_ADDR */
+                if (ioctl(fd, I2C_TENBIT, addr) < 0) {
+                    goto err;
+                }
+            }
+            else {
+                if (ioctl(fd, I2C_SLAVE, addr) < 0) {
+                    goto err;
+                }
+            }
+            break;
+
+        default:
+            return -ENOTSUP;
+            
+    }
+    return 0;
+err:
+    return -ENOTSUP;
+}
+
+static void qmp_chardev_open_i2c(Chardev *chr, ChardevBackend *backend,
+                                 bool *be_opened, Error **errp)
+{
+    ChardevI2c *i2c = backend->u.i2c.data;
+    void *addr;
+    int fd;
+
+    fd = qmp_chardev_open_file_source(i2c->device, O_RDWR | O_NONBLOCK,
+                                      errp);
+    if (fd < 0) {
+       return;
+    }
+    qemu_set_block(fd);
+    qemu_chr_open_fd(chr, fd, fd);
+    addr = (void *) (long) i2c->address;
+    i2c_ioctl(chr, CHR_IOCTL_I2C_SET_ADDR, addr);
+}
+
+static void qemu_chr_parse_i2c(QemuOpts *opts, ChardevBackend *backend, Error **errp)
+{
+    const char *device = qemu_opt_get(opts, "path");
+    const char *addr = qemu_opt_get(opts, "address");
+    long address;
+    ChardevI2c *i2c;
+    
+    if (device == NULL) {
+        error_setg(errp, "chardev: linux-i2c: no device path given");
+        return;
+    }
+    if (addr == NULL) {
+        error_setg(errp, "chardev: linux-i2c: no device address given");
+        return;
+    }
+    address = strtol(addr, NULL, 0);
+    if (address < 0 || address > CHR_I2C_ADDR_10BIT_MAX) {
+        error_setg(errp, "chardev: linux-i2c: invalid device address given");
+        return;
+    }
+    backend->type = CHARDEV_BACKEND_KIND_I2C;
+    i2c = backend->u.i2c.data = g_new0(ChardevI2c, 1);
+    qemu_chr_parse_common(opts, qapi_ChardevI2c_base(i2c));
+    i2c->device = g_strdup(device);
+    i2c->address = (int16_t) address;
+}
+
+static void char_i2c_class_init(ObjectClass *oc, void *data)
+{
+    ChardevClass *cc = CHARDEV_CLASS(oc);
+
+    cc->parse = qemu_chr_parse_i2c;
+    cc->open =  qmp_chardev_open_i2c;
+    cc->chr_ioctl = i2c_ioctl;
+}
+
+static const TypeInfo char_i2c_type_info = {
+    .name = TYPE_CHARDEV_I2C,
+    .parent = TYPE_CHARDEV_FD,
+    .class_init = char_i2c_class_init,
+};
+
+static void register_types(void)
+{
+    type_register_static(&char_i2c_type_info);
+}
+
+type_init(register_types);
diff --git a/chardev/char.c b/chardev/char.c
index 54724a56b1..93732a9909 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -926,6 +926,9 @@ QemuOptsList qemu_chardev_opts = {
         },{
             .name = "logappend",
             .type = QEMU_OPT_BOOL,
+        },{
+            .name = "address",
+            .type = QEMU_OPT_STRING,
         },
         { /* end of list */ }
     },
diff --git a/include/chardev/char.h b/include/chardev/char.h
index c0b57f7685..880614391f 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -245,6 +245,7 @@ int qemu_chr_wait_connected(Chardev *chr, Error **errp);
 #define TYPE_CHARDEV_SERIAL "chardev-serial"
 #define TYPE_CHARDEV_SOCKET "chardev-socket"
 #define TYPE_CHARDEV_UDP "chardev-udp"
+#define TYPE_CHARDEV_I2C "chardev-linux-i2c"
 
 #define CHARDEV_IS_RINGBUF(chr) \
     object_dynamic_cast(OBJECT(chr), TYPE_CHARDEV_RINGBUF)
diff --git a/qapi/char.json b/qapi/char.json
index a6e81ac7bc..602b4099dc 100644
--- a/qapi/char.json
+++ b/qapi/char.json
@@ -240,6 +240,21 @@
   'data': { 'device': 'str' },
   'base': 'ChardevCommon' }
 
+##
+# @ChardevI2c:
+#
+# Configuration info for i2c chardev (only on linux).
+#
+# @device: The name of the special file for the device,
+#          i.e. /dev/i2c-0 on linux
+# @address: The address of the i2c device on the host.
+#
+##
+{ 'struct': 'ChardevI2c',
+  'data': { 'device': 'str',
+            'address': 'int16'},
+  'base': 'ChardevCommon'}
+
 ##
 # @ChardevSocket:
 #
@@ -398,6 +413,7 @@
   'data': { 'file': 'ChardevFile',
             'serial': 'ChardevHostdev',
             'parallel': 'ChardevHostdev',
+            'i2c': 'ChardevI2c',
             'pipe': 'ChardevHostdev',
             'socket': 'ChardevSocket',
             'udp': 'ChardevUdp',
-- 
2.14.2

On 5/3/19 2:31 PM, Ernest Esene wrote:
> Add support for Linux I2C character device for I2C device passthrough
> For example:
> -chardev linux-i2c,address=0x46,path=/dev/i2c-N,id=i2c-chardev
> 
> Signed-off-by: Ernest Esene <eroken1@gmail.com>
> ---

Just an interface review:

> +++ b/qapi/char.json
> @@ -240,6 +240,21 @@
>    'data': { 'device': 'str' },
>    'base': 'ChardevCommon' }
>  
> +##
> +# @ChardevI2c:
> +#
> +# Configuration info for i2c chardev (only on linux).

Rather than a parenthetical comment, you could use:

> +#
> +# @device: The name of the special file for the device,
> +#          i.e. /dev/i2c-0 on linux
> +# @address: The address of the i2c device on the host.
> +#
> +##

Missing a 'Since: 4.1' line.

> +{ 'struct': 'ChardevI2c',
> +  'data': { 'device': 'str',
> +            'address': 'int16'},
> +  'base': 'ChardevCommon'}

'if': 'defined(CONFIG_LINUX)'

as part of the usage of this struct, so that introspection will only see
the struct where it can be used.

> +
>  ##
>  # @ChardevSocket:
>  #
> @@ -398,6 +413,7 @@
>    'data': { 'file': 'ChardevFile',
>              'serial': 'ChardevHostdev',
>              'parallel': 'ChardevHostdev',
> +            'i2c': 'ChardevI2c',
>              'pipe': 'ChardevHostdev',
>              'socket': 'ChardevSocket',
>              'udp': 'ChardevUdp',
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

On Fri, May 03, 2019 at 03:24:06PM -0500, Eric Blake wrote:
> On 5/3/19 2:31 PM, Ernest Esene wrote:
> > Add support for Linux I2C character device for I2C device passthrough
> > For example:
> > -chardev linux-i2c,address=0x46,path=/dev/i2c-N,id=i2c-chardev
> > 
> > Signed-off-by: Ernest Esene <eroken1@gmail.com>
> > ---
> 
> Just an interface review:
> 
> > +++ b/qapi/char.json
> > @@ -240,6 +240,21 @@
> >    'data': { 'device': 'str' },
> >    'base': 'ChardevCommon' }
> >  
> Missing a 'Since: 4.1' line.
4.1? Oh! I couldn't guess this number, I had to deliberately omit it.
> 
> > +{ 'struct': 'ChardevI2c',
> > +  'data': { 'device': 'str',
> > +            'address': 'int16'},
> > +  'base': 'ChardevCommon'}
> 
> 'if': 'defined(CONFIG_LINUX)'
> 
> as part of the usage of this struct, so that introspection will only see
> the struct where it can be used.
> 
> > +
> >  ##
> >  # @ChardevSocket:
> >  #
> > @@ -398,6 +413,7 @@
> >    'data': { 'file': 'ChardevFile',
> >              'serial': 'ChardevHostdev',
> >              'parallel': 'ChardevHostdev',
> > +            'i2c': 'ChardevI2c',
> >              'pipe': 'ChardevHostdev',
> >              'socket': 'ChardevSocket',
> >              'udp': 'ChardevUdp',
> > 
> 
> -- 
> Eric Blake, Principal Software Engineer
> Red Hat, Inc.           +1-919-301-3226
> Virtualization:  qemu.org | libvirt.org
> 
Thanks so much for the useful review. I have applied the changes and
will soon send v2 of the patch.

I hope it is OK to update the "MAINTAINERS" file this

Character Devices (Linux I2C)
M: Ernest Esene <eroken1@gmail.com>
S: Maintained
F: chardev/char-i2c.c


-Ernest Esene