include/hw/ssi/ssi.h

   1 /* QEMU Synchronous Serial Interface support.  */
   2
   3 /* In principle SSI is a point-point interface.  As such the qemu
   4    implementation has a single slave device on a "bus".
   5    However it is fairly common for boards to have multiple slaves
   6    connected to a single master, and select devices with an external
   7    chip select.  This is implemented in qemu by having an explicit mux device.
   8    It is assumed that master and slave are both using the same transfer width.
   9    */
  10
  11 #ifndef QEMU_SSI_H
  12 #define QEMU_SSI_H
  13
  14 #include "hw/qdev-core.h"
  15
  16 typedef struct SSISlave SSISlave;
  17 typedef struct SSISlaveClass SSISlaveClass;
  18 typedef enum SSICSMode SSICSMode;
  19
  20 #define TYPE_SSI_SLAVE "ssi-slave"
  21 #define SSI_SLAVE(obj) \
  22      OBJECT_CHECK(SSISlave, (obj), TYPE_SSI_SLAVE)
  23 #define SSI_SLAVE_CLASS(klass) \
  24      OBJECT_CLASS_CHECK(SSISlaveClass, (klass), TYPE_SSI_SLAVE)
  25 #define SSI_SLAVE_GET_CLASS(obj) \
  26      OBJECT_GET_CLASS(SSISlaveClass, (obj), TYPE_SSI_SLAVE)
  27
  28 #define SSI_GPIO_CS "ssi-gpio-cs"
  29
  30 enum SSICSMode {
  31     SSI_CS_NONE = 0,
  32     SSI_CS_LOW,
  33     SSI_CS_HIGH,
  34 };
  35
  36 /* Slave devices.  */
  37 struct SSISlaveClass {
  38     DeviceClass parent_class;
  39
  40     void (*realize)(SSISlave *dev, Error **errp);
  41
  42     /* if you have standard or no CS behaviour, just override transfer.
  43      * This is called when the device cs is active (true by default).
  44      */
  45     uint32_t (*transfer)(SSISlave *dev, uint32_t val);
  46     /* called when the CS line changes. Optional, devices only need to implement
  47      * this if they have side effects associated with the cs line (beyond
  48      * tristating the txrx lines).
  49      */
  50     int (*set_cs)(SSISlave *dev, bool select);
  51     /* define whether or not CS exists and is active low/high */
  52     SSICSMode cs_polarity;
  53
  54     /* if you have non-standard CS behaviour override this to take control
  55      * of the CS behaviour at the device level. transfer, set_cs, and
  56      * cs_polarity are unused if this is overwritten. Transfer_raw will
  57      * always be called for the device for every txrx access to the parent bus
  58      */
  59     uint32_t (*transfer_raw)(SSISlave *dev, uint32_t val);
  60 };
  61
  62 struct SSISlave {
  63     DeviceState parent_obj;
  64
  65     /* Chip select state */
  66     bool cs;
  67 };
  68
  69 extern const VMStateDescription vmstate_ssi_slave;
  70
  71 #define VMSTATE_SSI_SLAVE(_field, _state) {                          \
  72     .name       = (stringify(_field)),                               \
  73     .size       = sizeof(SSISlave),                                  \
  74     .vmsd       = &vmstate_ssi_slave,                                \
  75     .flags      = VMS_STRUCT,                                        \
  76     .offset     = vmstate_offset_value(_state, _field, SSISlave),    \
  77 }
  78
  79 DeviceState *ssi_create_slave(SSIBus *bus, const char *name);
  80 /**
  81  * ssi_realize_and_unref: realize and unref an SSI slave device
  82  * @dev: SSI slave device to realize
  83  * @bus: SSI bus to put it on
  84  * @errp: error pointer
  85  *
  86  * Call 'realize' on @dev, put it on the specified @bus, and drop the
  87  * reference to it. Errors are reported via @errp and by returning
  88  * false.
  89  *
  90  * This function is useful if you have created @dev via qdev_new()
  91  * (which takes a reference to the device it returns to you), so that
  92  * you can set properties on it before realizing it. If you don't need
  93  * to set properties then ssi_create_slave() is probably better (as it
  94  * does the create, init and realize in one step).
  95  *
  96  * If you are embedding the SSI slave into another QOM device and
  97  * initialized it via some variant on object_initialize_child() then
  98  * do not use this function, because that family of functions arrange
  99  * for the only reference to the child device to be held by the parent
 100  * via the child<> property, and so the reference-count-drop done here
 101  * would be incorrect.  (Instead you would want ssi_realize(), which
 102  * doesn't currently exist but would be trivial to create if we had
 103  * any code that wanted it.)
 104  */
 105 bool ssi_realize_and_unref(DeviceState *dev, SSIBus *bus, Error **errp);
 106
 107 /* Master interface.  */
 108 SSIBus *ssi_create_bus(DeviceState *parent, const char *name);
 109
 110 uint32_t ssi_transfer(SSIBus *bus, uint32_t val);
 111
 112 #endif