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[GitHub] [tvm-rfcs] Mousius commented on a change in pull request #31: C Device API
Mousius commented on a change in pull request #31:
URL: https://github.com/apache/tvm-rfcs/pull/31#discussion_r714036291
##########
File path: rfcs/0031-devices-api.md
##########
@@ -0,0 +1,363 @@
+- Feature Name: C Device API
+- Start Date: 02-08-2021
+- RFC PR: [apache/tvm-rfcs#31](https://github.com/apache/tvm-rfcs/pull/31)
+- GitHub Issue: [apache/tvm#0000](https://github.com/apache/tvm/issues/0000)
+
+
+# Summary
+[summary]: #summary
+This RFC aims to provide an API which can be used by the C runtime to abstract the variety of driver APIs for different platforms. This is specifically catering towards RTOS abstractions for embedded device drivers and aims to implement a subset of the overall Device API with supporting infrastructure to enable future expansion.
+
+# Motivation
+[motivation]: #motivation
+
+When using an accelerator, such as the [Arm® Ethos™-U](https://github.com/apache/tvm-rfcs/pull/11), an Embedded Real-Time Operating System (RTOS) will provide a device abstraction to access the device resource. When using these abstractions, TVM needs to understand how to interact with a device for a given platform.
+
+Taking the common example of a UART interface (imagining the accelerator is communicated to via this interface); in Zephyr, this would look similar to:
+
+```c
+#include <zephyr.h>
+#include <device.h>
+
+struct device *uart_dev = device_get_binding("USART0");
+
+char data[] = "Hello World!\r\n";
+uart_tx(uart_dev, data, sizeof(data), 100);
+```
+
+Whereas in CMSIS, this would look more similar to:
+
+```c
+ARM_DRIVER_USART* uart_dev = &Driver_USART0;
+uart_dev->Initialize(NULL);
+
+char data[] = "Hello World!\r\n";
+uart_dev->Send(data, sizeof(data)/sizeof(data[0]));
+```
+
+In this example, you can see the diversity of RTOS implementations for drivers and why it's required to provide a flexible abstraction to pass devices for micro targets.
+
+# Guide-level explanation
+[guide-level-explanation]: #guide-level-explanation
+
+## User App
+`tvm_device_<device>_t`s are implemented for each RTOS or platform required, these are included by the user who chooses as appropriate for their application. Notably, to avoid dynamic allocation, the user must provide the `tvm_device_<device>_t` struct and initialise it rather than it being created and setup for them in the API. This is augmented by named functions for each device, examples in the case of the "woofles" accelerator:
+
+```c
+typedef void* tvm_device_woofles_t; // Called by User App
+int32_t TVMDeviceWooflesInit(tvm_device_woofles_t* tvm_dev, ...); // Called by User App
+int32_t TVMDeviceWooflesActivate(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesOpen(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesClose(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesDeactivate(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesDestroy(tvm_device_woofles_t* tvm_dev); // Called by User App
+```
+
+Which is implemented as part of a User App:
+```c
+#include <tvm/runtime/device.h>
+#include <tvm/device/woofles/zephyr.h>
+
+struct device* woofles_zephyr_device = device_get_binding("WOOFLES0");
+tvm_device_woofles_t accelerator; // Opaque type for accelerator device
+TVMDeviceWooflesInit(&accelerator, woofles_zephyr_device);
+
+struct tvmgen_mynetwork_devices devices {
+ .accelerator = accelerator
+};
+
+int32_t ret = tvmgen_mynetwork_run(
+ ...,
+ &devices
+);
+
+TVMDeviceDestroy(&accelerator);
+```
+
+## Platform Structures
+Users can take a implementations from `src/runtime/crt/device` and headers from `include/runtime/crt/device` which maps to their platform device implementation. In the case of a bare metal environment, this would default to a void pointer as there's no information available.
+
+```c
+typedef tvm_device_woofles_t void*;
+```
+
+For RTOS implementations, a structure can be created such as this simple Zephyr wrapper (include/runtime/crt/platform/zephyr.h):
+
+```c
+#include <device.h>
+
+typedef struct {
+ struct device* dev;
+} tvm_device_woofles_t;
+```
+
+This enables the OS maximum control over the resources required and provides the opportunity to craft code in whichever way is most idiomatic for that platform, such as if an additional locking mechanism is required:
+
+```c
+#include <device.h>
+#include <kernel.h>
+
+typedef struct {
+ struct device* dev;
+ k_mutex lock;
+} tvm_device_woofles_t;
+```
+
+## Generic Device API
+The majority of the device API calls should be added to the platform-agnostic `<device>.h`:
+```c
+int32_t TVMDeviceWooflesActivate(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesOpen(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesClose(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesDeactivate(tvm_device_woofles_t* tvm_dev); // Called by generated code
+```
+
+These can all be implemented using the user-opaque context `tvm_device_<device>_t*`, enabling the majority of TVM code to be portable between RTOS implementations; importantly this applies to those called within operator functions (see below). The executors are agnostic to the underlying device implementation and simply get passed the relevant device pointer which is then passed to the correct symbol.
+
+## Platform Device API
+To allow setting of platform specifics into the opaque struct, these should be defined in the platform header. Alongside the header, an additional file will provide implementations (`src/runtime/crt/device/<device>/<platform>.c`):
+```c
+int32_t TVMDeviceWooflesInit(tvm_device_t* tvm_dev, struct device* zephyr_dev) {
+ tvm_dev->device = zephyr_dev;
+}
+```
+This simple wrapper enables type checking of these functions and defining a clear translation boundary between the underlying OS implementation and TVM.
+
+# Reference-level explanation
+[reference-level-explanation]: #reference-level-explanation
+
+## Entrypoint
+The entrypoint API defined in [Embedded C Runtime Interface](https://discuss.tvm.apache.org/t/rfc-utvm-embedded-c-runtime-interface/9951) is augmented with the `devices` structure which contains implemented `tvm_device_t` `struct`s for each device used by the network:
+```
+typedef struct {
+ struct tvm_device_woofles_t* woofles
+} tvmgen_mynetwork_devices;
+```
+
+These are re-cast to `void *` when entering the AOT main function to pass it without TIR understanding the struct types.
+
+```c
+int32_t tvmgen_mynetwork_run(
+ ...,
+ struct tvmgen_mynetwork_devices* devices
+) {
+ tvmgen_mynetwork_run_model(
+ ...,
+ devices->host,
+ devices->accelerator
+ );
+}
+```
+
+## Executor Function
+Each operator is provided with a single device object which can be abstracted and passed as the `void* resource_handle`. The main function calls into the device API to setup and teardown resources before and after each operator call.
+
+```c
+int32_t tvmgen_mynetwork_run_model(..., device0, device1) {
+ TVMDeviceWooflesActivate(device0); // Could reserve or enable certain circuitry ahead of time
Review comment:
I added some words to that effect, essentially stating that the memory flow is outside this RFC as it stands right now but we should be aware that means it could happen at any time.
##########
File path: rfcs/0031-devices-api.md
##########
@@ -0,0 +1,363 @@
+- Feature Name: C Device API
+- Start Date: 02-08-2021
+- RFC PR: [apache/tvm-rfcs#31](https://github.com/apache/tvm-rfcs/pull/31)
+- GitHub Issue: [apache/tvm#0000](https://github.com/apache/tvm/issues/0000)
+
+
+# Summary
+[summary]: #summary
+This RFC aims to provide an API which can be used by the C runtime to abstract the variety of driver APIs for different platforms. This is specifically catering towards RTOS abstractions for embedded device drivers and aims to implement a subset of the overall Device API with supporting infrastructure to enable future expansion.
+
+# Motivation
+[motivation]: #motivation
+
+When using an accelerator, such as the [Arm® Ethos™-U](https://github.com/apache/tvm-rfcs/pull/11), an Embedded Real-Time Operating System (RTOS) will provide a device abstraction to access the device resource. When using these abstractions, TVM needs to understand how to interact with a device for a given platform.
+
+Taking the common example of a UART interface (imagining the accelerator is communicated to via this interface); in Zephyr, this would look similar to:
+
+```c
+#include <zephyr.h>
+#include <device.h>
+
+struct device *uart_dev = device_get_binding("USART0");
+
+char data[] = "Hello World!\r\n";
+uart_tx(uart_dev, data, sizeof(data), 100);
+```
+
+Whereas in CMSIS, this would look more similar to:
+
+```c
+ARM_DRIVER_USART* uart_dev = &Driver_USART0;
+uart_dev->Initialize(NULL);
+
+char data[] = "Hello World!\r\n";
+uart_dev->Send(data, sizeof(data)/sizeof(data[0]));
+```
+
+In this example, you can see the diversity of RTOS implementations for drivers and why it's required to provide a flexible abstraction to pass devices for micro targets.
+
+# Guide-level explanation
+[guide-level-explanation]: #guide-level-explanation
+
+## User App
+`tvm_device_<device>_t`s are implemented for each RTOS or platform required, these are included by the user who chooses as appropriate for their application. Notably, to avoid dynamic allocation, the user must provide the `tvm_device_<device>_t` struct and initialise it rather than it being created and setup for them in the API. This is augmented by named functions for each device, examples in the case of the "woofles" accelerator:
+
+```c
+typedef void* tvm_device_woofles_t; // Called by User App
+int32_t TVMDeviceWooflesInit(tvm_device_woofles_t* tvm_dev, ...); // Called by User App
+int32_t TVMDeviceWooflesActivate(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesOpen(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesClose(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesDeactivate(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesDestroy(tvm_device_woofles_t* tvm_dev); // Called by User App
+```
+
+Which is implemented as part of a User App:
+```c
+#include <tvm/runtime/device.h>
+#include <tvm/device/woofles/zephyr.h>
+
+struct device* woofles_zephyr_device = device_get_binding("WOOFLES0");
+tvm_device_woofles_t accelerator; // Opaque type for accelerator device
+TVMDeviceWooflesInit(&accelerator, woofles_zephyr_device);
+
+struct tvmgen_mynetwork_devices devices {
+ .accelerator = accelerator
+};
+
+int32_t ret = tvmgen_mynetwork_run(
+ ...,
+ &devices
+);
+
+TVMDeviceDestroy(&accelerator);
+```
+
+## Platform Structures
+Users can take a implementations from `src/runtime/crt/device` and headers from `include/runtime/crt/device` which maps to their platform device implementation. In the case of a bare metal environment, this would default to a void pointer as there's no information available.
+
+```c
+typedef tvm_device_woofles_t void*;
+```
+
+For RTOS implementations, a structure can be created such as this simple Zephyr wrapper (include/runtime/crt/platform/zephyr.h):
+
+```c
+#include <device.h>
+
+typedef struct {
+ struct device* dev;
+} tvm_device_woofles_t;
+```
+
+This enables the OS maximum control over the resources required and provides the opportunity to craft code in whichever way is most idiomatic for that platform, such as if an additional locking mechanism is required:
+
+```c
+#include <device.h>
+#include <kernel.h>
+
+typedef struct {
+ struct device* dev;
+ k_mutex lock;
+} tvm_device_woofles_t;
+```
+
+## Generic Device API
+The majority of the device API calls should be added to the platform-agnostic `<device>.h`:
+```c
+int32_t TVMDeviceWooflesActivate(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesOpen(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesClose(tvm_device_woofles_t* tvm_dev); // Called by generated code
+int32_t TVMDeviceWooflesDeactivate(tvm_device_woofles_t* tvm_dev); // Called by generated code
+```
+
+These can all be implemented using the user-opaque context `tvm_device_<device>_t*`, enabling the majority of TVM code to be portable between RTOS implementations; importantly this applies to those called within operator functions (see below). The executors are agnostic to the underlying device implementation and simply get passed the relevant device pointer which is then passed to the correct symbol.
+
+## Platform Device API
+To allow setting of platform specifics into the opaque struct, these should be defined in the platform header. Alongside the header, an additional file will provide implementations (`src/runtime/crt/device/<device>/<platform>.c`):
+```c
+int32_t TVMDeviceWooflesInit(tvm_device_t* tvm_dev, struct device* zephyr_dev) {
+ tvm_dev->device = zephyr_dev;
+}
+```
+This simple wrapper enables type checking of these functions and defining a clear translation boundary between the underlying OS implementation and TVM.
+
+# Reference-level explanation
+[reference-level-explanation]: #reference-level-explanation
+
+## Entrypoint
+The entrypoint API defined in [Embedded C Runtime Interface](https://discuss.tvm.apache.org/t/rfc-utvm-embedded-c-runtime-interface/9951) is augmented with the `devices` structure which contains implemented `tvm_device_t` `struct`s for each device used by the network:
+```
+typedef struct {
+ struct tvm_device_woofles_t* woofles
+} tvmgen_mynetwork_devices;
+```
+
+These are re-cast to `void *` when entering the AOT main function to pass it without TIR understanding the struct types.
+
+```c
+int32_t tvmgen_mynetwork_run(
+ ...,
+ struct tvmgen_mynetwork_devices* devices
+) {
+ tvmgen_mynetwork_run_model(
+ ...,
+ devices->host,
Review comment:
`tvm_struct_get` is a special case intrinsic for accessing TVM structs, it sadly doesn't work in this general way :crying_cat_face:
##########
File path: rfcs/0031-devices-api.md
##########
@@ -0,0 +1,363 @@
+- Feature Name: C Device API
+- Start Date: 02-08-2021
+- RFC PR: [apache/tvm-rfcs#31](https://github.com/apache/tvm-rfcs/pull/31)
+- GitHub Issue: [apache/tvm#0000](https://github.com/apache/tvm/issues/0000)
+
+
+# Summary
+[summary]: #summary
+This RFC aims to provide an API which can be used by the C runtime to abstract the variety of driver APIs for different platforms. This is specifically catering towards RTOS abstractions for embedded device drivers and aims to implement a subset of the overall Device API with supporting infrastructure to enable future expansion.
+
+# Motivation
+[motivation]: #motivation
+
+When using an accelerator, such as the [Arm® Ethos™-U](https://github.com/apache/tvm-rfcs/pull/11), an Embedded Real-Time Operating System (RTOS) will provide a device abstraction to access the device resource. When using these abstractions, TVM needs to understand how to interact with a device for a given platform.
+
+Taking the common example of a UART interface (imagining the accelerator is communicated to via this interface); in Zephyr, this would look similar to:
+
+```c
+#include <zephyr.h>
+#include <device.h>
+
+struct device *uart_dev = device_get_binding("USART0");
+
+char data[] = "Hello World!\r\n";
+uart_tx(uart_dev, data, sizeof(data), 100);
+```
+
+Whereas in CMSIS, this would look more similar to:
+
+```c
+ARM_DRIVER_USART* uart_dev = &Driver_USART0;
+uart_dev->Initialize(NULL);
+
+char data[] = "Hello World!\r\n";
+uart_dev->Send(data, sizeof(data)/sizeof(data[0]));
+```
+
+In this example, you can see the diversity of RTOS implementations for drivers and why it's required to provide a flexible abstraction to pass devices for micro targets.
+
+# Guide-level explanation
+[guide-level-explanation]: #guide-level-explanation
+
+## User App
+`tvm_device_<device>_t`s are implemented for each RTOS or platform required, these are included by the user who chooses as appropriate for their application. Notably, to avoid dynamic allocation, the user must provide the `tvm_device_<device>_t` struct and initialise it rather than it being created and setup for them in the API. This is augmented by named functions for each device, examples in the case of the "woofles" accelerator:
+
+```c
Review comment:
I think this is included further down the RFC in the outline of an executor and explored further in future work? The hooks are intentionally kept simply named so they can be interpreted for a device, from my experience the `TVMDeviceWooflesActivate` could span from setting a pin high to sending a series of commands over a communications bus? The main thing I'm trying to communicate is that `Activate` is called before `Open` which is documented in the executor flow, this might not be the best way of demonstrating it though so please feel free to suggest an alternative.
##########
File path: rfcs/0031-devices-api.md
##########
@@ -0,0 +1,363 @@
+- Feature Name: C Device API
+- Start Date: 02-08-2021
+- RFC PR: [apache/tvm-rfcs#31](https://github.com/apache/tvm-rfcs/pull/31)
+- GitHub Issue: [apache/tvm#0000](https://github.com/apache/tvm/issues/0000)
+
+
+# Summary
+[summary]: #summary
+This RFC aims to provide an API which can be used by the C runtime to abstract the variety of driver APIs for different platforms. This is specifically catering towards RTOS abstractions for embedded device drivers and aims to implement a subset of the overall Device API with supporting infrastructure to enable future expansion.
+
+# Motivation
+[motivation]: #motivation
+
+When using an accelerator, such as the [Arm® Ethos™-U](https://github.com/apache/tvm-rfcs/pull/11), an Embedded Real-Time Operating System (RTOS) will provide a device abstraction to access the device resource. When using these abstractions, TVM needs to understand how to interact with a device for a given platform.
+
+Taking the common example of a UART interface (imagining the accelerator is communicated to via this interface); in Zephyr, this would look similar to:
+
+```c
+#include <zephyr.h>
+#include <device.h>
+
+struct device *uart_dev = device_get_binding("USART0");
+
+char data[] = "Hello World!\r\n";
+uart_tx(uart_dev, data, sizeof(data), 100);
+```
+
+Whereas in CMSIS, this would look more similar to:
+
+```c
+ARM_DRIVER_USART* uart_dev = &Driver_USART0;
+uart_dev->Initialize(NULL);
+
+char data[] = "Hello World!\r\n";
+uart_dev->Send(data, sizeof(data)/sizeof(data[0]));
+```
+
+In this example, you can see the diversity of RTOS implementations for drivers and why it's required to provide a flexible abstraction to pass devices for micro targets.
+
+# Guide-level explanation
+[guide-level-explanation]: #guide-level-explanation
+
+## User App
+`tvm_device_<device>_t`s are implemented for each RTOS or platform required, these are included by the user who chooses as appropriate for their application. Notably, to avoid dynamic allocation, the user must provide the `tvm_device_<device>_t` struct and initialise it rather than it being created and setup for them in the API. This is augmented by named functions for each device, examples in the case of the "woofles" accelerator:
Review comment:
I've tweaked it a bit :smile_cat:
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