Re: [PATCH v6 1/5] hw/nvram/fw_cfg: Add the FW_CFG_DATA_GENERATOR interface
On 5/20/20 12:01 AM, Laszlo Ersek wrote:
> On 05/19/20 20:20, Philippe Mathieu-Daudé wrote:
>> The FW_CFG_DATA_GENERATOR allow any object to product
>
> (1) I suggest:
>
> s/allow/allows/
> s/product/produce/
>
>> blob of data consumable by the fw_cfg device.
>>
>> Signed-off-by: Philippe Mathieu-Daudé
>> ---
>> include/hw/nvram/fw_cfg.h | 49 +++
>> hw/nvram/fw_cfg.c | 30
>> 2 files changed, 79 insertions(+)
>>
>> diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
>> index 25d9307018..74b4790fae 100644
>> --- a/include/hw/nvram/fw_cfg.h
>> +++ b/include/hw/nvram/fw_cfg.h
>> @@ -9,11 +9,40 @@
>> #define TYPE_FW_CFG "fw_cfg"
>> #define TYPE_FW_CFG_IO "fw_cfg_io"
>> #define TYPE_FW_CFG_MEM "fw_cfg_mem"
>> +#define TYPE_FW_CFG_DATA_GENERATOR_INTERFACE "fw_cfg-data-generator"
>>
>> #define FW_CFG(obj) OBJECT_CHECK(FWCfgState,(obj), TYPE_FW_CFG)
>> #define FW_CFG_IO(obj) OBJECT_CHECK(FWCfgIoState, (obj), TYPE_FW_CFG_IO)
>> #define FW_CFG_MEM(obj) OBJECT_CHECK(FWCfgMemState, (obj), TYPE_FW_CFG_MEM)
>>
>> +#define FW_CFG_DATA_GENERATOR_CLASS(class) \
>> +OBJECT_CLASS_CHECK(FWCfgDataGeneratorClass, (class), \
>> + TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)
>> +#define FW_CFG_DATA_GENERATOR_GET_CLASS(obj) \
>> +OBJECT_GET_CLASS(FWCfgDataGeneratorClass, (obj), \
>> + TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)
>> +
>> +typedef struct FWCfgDataGeneratorClass {
>> +/*< private >*/
>> +InterfaceClass parent_class;
>> +/*< public >*/
>> +
>> +/**
>> + * get_data:
>> + * @obj: the object implementing this interface
>> + *
>> + * Returns: pointer to start of the generated item data
>> + */
>> +const void *(*get_data)(Object *obj);
>
> I'm not familiar with QOM, so please excuse any dumb questions.
>
> "const" suggests the blob returned remains owned by "obj";
Yes, it is owned by the generator object.
fw_cfg_add_from_generator() does a memdup().
> that answers
> the question whether the caller should attempt to free the blob. (The
> answer is "no".)
>
> (2) However, will this perhaps expose other functions, currently taking
> non-const-qualified pointers, to which we'd like to pass the blob
> returned by the above member function?
>
> Because, then we'd have to cast away "const",
It is illegal to cast away "const". This is why I choose to use it here,
if the consumer want to modify it, it is forced to make its own copy.
> and I find that much
> uglier than removing the "const" from *here*, and adding a more verbose
> comment as replacement.
>
> Yes, this is clearly speculation -- IOW just a question. If all the
> functions we're going to pass the return value to are fine with
> pointer-to-const, then this interface should be OK.
The only user so far uses memdup().
>
> (Obviously when I say "cast away const", I think of functions that do
> not actually modify the object pointed-to by the non-const-qualified
> pointer.)
>
>> +/**
>> + * get_length:
>> + * @obj: the object implementing this interface
>> + *
>> + * Returns: the size of the generated item data in bytes
>> + */
>> +size_t (*get_length)(Object *obj);
>> +} FWCfgDataGeneratorClass;
>> +
>> typedef struct fw_cfg_file FWCfgFile;
>>
>> #define FW_CFG_ORDER_OVERRIDE_VGA70
>> @@ -263,6 +292,26 @@ void fw_cfg_add_file_callback(FWCfgState *s, const char
>> *filename,
>> void *fw_cfg_modify_file(FWCfgState *s, const char *filename, void *data,
>> size_t len);
>>
>> +/**
>> + * fw_cfg_add_from_generator:
>> + * @s: fw_cfg device being modified
>> + * @filename: name of new fw_cfg file item
>> + * @generator_id: name of object implementing FW_CFG_DATA_GENERATOR
>> interface
>> + * @errp: pointer to a NULL initialized error object
>> + *
>> + * Add a new NAMED fw_cfg item with the content generated from the
>> + * @generator_id object. The data referenced by the starting pointer is
>> copied
>
> (3) s/referenced by the starting pointer/generated by the @generator_id
> object/
>
>> + * into the data structure of the fw_cfg device.
>> + * The next available (unused) selector key starting at FW_CFG_FILE_FIRST
>> + * will be used; also, a new entry will be added to the file directory
>> + * structure residing at key value FW_CFG_FILE_DIR, containing the item
>> name,
>> + * data size, and assigned selector key value.
>> + *
>> + * Returns: the size of the generated item data on success, -1 otherwise.
>
> (4) I don't like ssize_t for a return value like this.
>
> First, get_length() returns size_t, which may not be representable in an
> ssize_t.
>
> (Actually, it's worse than that; POSIX says, "the type ssize_t shall be
> capable of storing values at least in the range [-1, {SSIZE_MAX}]" --
> and if I run "getconf SSIZE_MAX", I get 32767. Indeed, _POSIX_SSIZE_MAX,
> which is the minimum for any
Re: [PATCH v6 1/5] hw/nvram/fw_cfg: Add the FW_CFG_DATA_GENERATOR interface
On 05/19/20 20:20, Philippe Mathieu-Daudé wrote:
> The FW_CFG_DATA_GENERATOR allow any object to product
(1) I suggest:
s/allow/allows/
s/product/produce/
> blob of data consumable by the fw_cfg device.
>
> Signed-off-by: Philippe Mathieu-Daudé
> ---
> include/hw/nvram/fw_cfg.h | 49 +++
> hw/nvram/fw_cfg.c | 30
> 2 files changed, 79 insertions(+)
>
> diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
> index 25d9307018..74b4790fae 100644
> --- a/include/hw/nvram/fw_cfg.h
> +++ b/include/hw/nvram/fw_cfg.h
> @@ -9,11 +9,40 @@
> #define TYPE_FW_CFG "fw_cfg"
> #define TYPE_FW_CFG_IO "fw_cfg_io"
> #define TYPE_FW_CFG_MEM "fw_cfg_mem"
> +#define TYPE_FW_CFG_DATA_GENERATOR_INTERFACE "fw_cfg-data-generator"
>
> #define FW_CFG(obj) OBJECT_CHECK(FWCfgState,(obj), TYPE_FW_CFG)
> #define FW_CFG_IO(obj) OBJECT_CHECK(FWCfgIoState, (obj), TYPE_FW_CFG_IO)
> #define FW_CFG_MEM(obj) OBJECT_CHECK(FWCfgMemState, (obj), TYPE_FW_CFG_MEM)
>
> +#define FW_CFG_DATA_GENERATOR_CLASS(class) \
> +OBJECT_CLASS_CHECK(FWCfgDataGeneratorClass, (class), \
> + TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)
> +#define FW_CFG_DATA_GENERATOR_GET_CLASS(obj) \
> +OBJECT_GET_CLASS(FWCfgDataGeneratorClass, (obj), \
> + TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)
> +
> +typedef struct FWCfgDataGeneratorClass {
> +/*< private >*/
> +InterfaceClass parent_class;
> +/*< public >*/
> +
> +/**
> + * get_data:
> + * @obj: the object implementing this interface
> + *
> + * Returns: pointer to start of the generated item data
> + */
> +const void *(*get_data)(Object *obj);
I'm not familiar with QOM, so please excuse any dumb questions.
"const" suggests the blob returned remains owned by "obj"; that answers
the question whether the caller should attempt to free the blob. (The
answer is "no".)
(2) However, will this perhaps expose other functions, currently taking
non-const-qualified pointers, to which we'd like to pass the blob
returned by the above member function?
Because, then we'd have to cast away "const", and I find that much
uglier than removing the "const" from *here*, and adding a more verbose
comment as replacement.
Yes, this is clearly speculation -- IOW just a question. If all the
functions we're going to pass the return value to are fine with
pointer-to-const, then this interface should be OK.
(Obviously when I say "cast away const", I think of functions that do
not actually modify the object pointed-to by the non-const-qualified
pointer.)
> +/**
> + * get_length:
> + * @obj: the object implementing this interface
> + *
> + * Returns: the size of the generated item data in bytes
> + */
> +size_t (*get_length)(Object *obj);
> +} FWCfgDataGeneratorClass;
> +
> typedef struct fw_cfg_file FWCfgFile;
>
> #define FW_CFG_ORDER_OVERRIDE_VGA70
> @@ -263,6 +292,26 @@ void fw_cfg_add_file_callback(FWCfgState *s, const char
> *filename,
> void *fw_cfg_modify_file(FWCfgState *s, const char *filename, void *data,
> size_t len);
>
> +/**
> + * fw_cfg_add_from_generator:
> + * @s: fw_cfg device being modified
> + * @filename: name of new fw_cfg file item
> + * @generator_id: name of object implementing FW_CFG_DATA_GENERATOR interface
> + * @errp: pointer to a NULL initialized error object
> + *
> + * Add a new NAMED fw_cfg item with the content generated from the
> + * @generator_id object. The data referenced by the starting pointer is
> copied
(3) s/referenced by the starting pointer/generated by the @generator_id
object/
> + * into the data structure of the fw_cfg device.
> + * The next available (unused) selector key starting at FW_CFG_FILE_FIRST
> + * will be used; also, a new entry will be added to the file directory
> + * structure residing at key value FW_CFG_FILE_DIR, containing the item name,
> + * data size, and assigned selector key value.
> + *
> + * Returns: the size of the generated item data on success, -1 otherwise.
(4) I don't like ssize_t for a return value like this.
First, get_length() returns size_t, which may not be representable in an
ssize_t.
(Actually, it's worse than that; POSIX says, "the type ssize_t shall be
capable of storing values at least in the range [-1, {SSIZE_MAX}]" --
and if I run "getconf SSIZE_MAX", I get 32767. Indeed, _POSIX_SSIZE_MAX,
which is the minimum for any implementation's SSIZE_MAX, is 32767.)
Second, is a zero-sized blob useful in fw_cfg (from a generator)?
If it is not useful, then this function should return size_t, and use
retval=0 for signaling an error.
If a zero-sized blob is useful, then the function should return a bool
(in addition to producing "errp"), and output the blob size as a
separate parameter.
> + */
> +ssize_t fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
> + const
[PATCH v6 1/5] hw/nvram/fw_cfg: Add the FW_CFG_DATA_GENERATOR interface
The FW_CFG_DATA_GENERATOR allow any object to product
blob of data consumable by the fw_cfg device.
Signed-off-by: Philippe Mathieu-Daudé
---
include/hw/nvram/fw_cfg.h | 49 +++
hw/nvram/fw_cfg.c | 30
2 files changed, 79 insertions(+)
diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
index 25d9307018..74b4790fae 100644
--- a/include/hw/nvram/fw_cfg.h
+++ b/include/hw/nvram/fw_cfg.h
@@ -9,11 +9,40 @@
#define TYPE_FW_CFG "fw_cfg"
#define TYPE_FW_CFG_IO "fw_cfg_io"
#define TYPE_FW_CFG_MEM "fw_cfg_mem"
+#define TYPE_FW_CFG_DATA_GENERATOR_INTERFACE "fw_cfg-data-generator"
#define FW_CFG(obj) OBJECT_CHECK(FWCfgState,(obj), TYPE_FW_CFG)
#define FW_CFG_IO(obj) OBJECT_CHECK(FWCfgIoState, (obj), TYPE_FW_CFG_IO)
#define FW_CFG_MEM(obj) OBJECT_CHECK(FWCfgMemState, (obj), TYPE_FW_CFG_MEM)
+#define FW_CFG_DATA_GENERATOR_CLASS(class) \
+OBJECT_CLASS_CHECK(FWCfgDataGeneratorClass, (class), \
+ TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)
+#define FW_CFG_DATA_GENERATOR_GET_CLASS(obj) \
+OBJECT_GET_CLASS(FWCfgDataGeneratorClass, (obj), \
+ TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)
+
+typedef struct FWCfgDataGeneratorClass {
+/*< private >*/
+InterfaceClass parent_class;
+/*< public >*/
+
+/**
+ * get_data:
+ * @obj: the object implementing this interface
+ *
+ * Returns: pointer to start of the generated item data
+ */
+const void *(*get_data)(Object *obj);
+/**
+ * get_length:
+ * @obj: the object implementing this interface
+ *
+ * Returns: the size of the generated item data in bytes
+ */
+size_t (*get_length)(Object *obj);
+} FWCfgDataGeneratorClass;
+
typedef struct fw_cfg_file FWCfgFile;
#define FW_CFG_ORDER_OVERRIDE_VGA70
@@ -263,6 +292,26 @@ void fw_cfg_add_file_callback(FWCfgState *s, const char
*filename,
void *fw_cfg_modify_file(FWCfgState *s, const char *filename, void *data,
size_t len);
+/**
+ * fw_cfg_add_from_generator:
+ * @s: fw_cfg device being modified
+ * @filename: name of new fw_cfg file item
+ * @generator_id: name of object implementing FW_CFG_DATA_GENERATOR interface
+ * @errp: pointer to a NULL initialized error object
+ *
+ * Add a new NAMED fw_cfg item with the content generated from the
+ * @generator_id object. The data referenced by the starting pointer is copied
+ * into the data structure of the fw_cfg device.
+ * The next available (unused) selector key starting at FW_CFG_FILE_FIRST
+ * will be used; also, a new entry will be added to the file directory
+ * structure residing at key value FW_CFG_FILE_DIR, containing the item name,
+ * data size, and assigned selector key value.
+ *
+ * Returns: the size of the generated item data on success, -1 otherwise.
+ */
+ssize_t fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
+ const char *generator_id, Error **errp);
+
FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
AddressSpace *dma_as);
FWCfgState *fw_cfg_init_io(uint32_t iobase);
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 8dd50c2c72..e18cb074df 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -1032,6 +1032,30 @@ void *fw_cfg_modify_file(FWCfgState *s, const char
*filename,
return NULL;
}
+ssize_t fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
+ const char *generator_id, Error **errp)
+{
+FWCfgDataGeneratorClass *k;
+Object *o;
+size_t sz;
+
+o = object_resolve_path_component(object_get_objects_root(), generator_id);
+if (!o) {
+error_setg(errp, "Cannot find object ID %s", generator_id);
+return -1;
+}
+if (!object_dynamic_cast(o, TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)) {
+error_setg(errp, "Object '%s' is not a fw_cfg-data-generator subclass",
+ generator_id);
+return -1;
+}
+k = FW_CFG_DATA_GENERATOR_GET_CLASS(o);
+sz = k->get_length(o);
+fw_cfg_add_file(s, filename, g_memdup(k->get_data(o), sz), sz);
+
+return sz;
+}
+
static void fw_cfg_machine_reset(void *opaque)
{
MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
@@ -1333,12 +1357,18 @@ static const TypeInfo fw_cfg_mem_info = {
.class_init= fw_cfg_mem_class_init,
};
+static const TypeInfo fw_cfg_data_generator_interface_info = {
+.name = TYPE_FW_CFG_DATA_GENERATOR_INTERFACE,
+.parent = TYPE_INTERFACE,
+.class_size = sizeof(FWCfgDataGeneratorClass),
+};
static void fw_cfg_register_types(void)
{
type_register_static(_cfg_info);
type_register_static(_cfg_io_info);
type_register_static(_cfg_mem_info);
+type_register_static(_cfg_data_generator_interface_info);
}
type_init(fw_cfg_register_types)
--
2.21.3
