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