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 110